Cache image feature and testing

24 files changed, 2945 insertions, 131 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 510db1e..b7cfeb2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -90,8 +90,10 @@ set (H5C_SOURCES
     ${HDF5_SRC_DIR}/H5C.c
     ${HDF5_SRC_DIR}/H5Cdbg.c
     ${HDF5_SRC_DIR}/H5Cepoch.c
+    ${HDF5_SRC_DIR}/H5Cimage.c
     ${HDF5_SRC_DIR}/H5Clog.c
     ${HDF5_SRC_DIR}/H5Cmpio.c
+    ${HDF5_SRC_DIR}/H5Cprefetched.c
     ${HDF5_SRC_DIR}/H5Cquery.c
     ${HDF5_SRC_DIR}/H5Ctag.c
     ${HDF5_SRC_DIR}/H5Ctest.c
@@ -439,6 +441,7 @@ set (H5O_SOURCES
     ${HDF5_SRC_DIR}/H5Obogus.c
     ${HDF5_SRC_DIR}/H5Obtreek.c
     ${HDF5_SRC_DIR}/H5Ocache.c
+    ${HDF5_SRC_DIR}/H5Ocache_image.c
     ${HDF5_SRC_DIR}/H5Ochunk.c
     ${HDF5_SRC_DIR}/H5Ocont.c
     ${HDF5_SRC_DIR}/H5Ocopy.c
diff --git a/src/H5AC.c b/src/H5AC.c
index a04b7be..6a38657 100644
--- a/src/H5AC.c
+++ b/src/H5AC.c
@@ -142,7 +142,8 @@ static const H5AC_class_t *const H5AC_class_s[] = {
     H5AC_SUPERBLOCK,            /* (25) file superblock                 */
     H5AC_DRVRINFO,              /* (26) driver info block (supplements superblock) */
     H5AC_EPOCH_MARKER,          /* (27) epoch marker - always internal to cache */
-    H5AC_PROXY_ENTRY            /* (28) cache entry proxy               */
+    H5AC_PROXY_ENTRY,           /* (28) cache entry proxy               */
+    H5AC_PREFETCHED_ENTRY  	/* (29) prefetched entry - always internal to cache */
 };
 
 
@@ -370,12 +371,13 @@ H5AC_term_package(void)
  *-------------------------------------------------------------------------
  */
 herr_t
-H5AC_create(const H5F_t *f, H5AC_cache_config_t *config_ptr)
+H5AC_create(const H5F_t *f, H5AC_cache_config_t *config_ptr, H5AC_cache_image_config_t * image_config_ptr)
 {
 #ifdef H5_HAVE_PARALLEL
     char 	 prefix[H5C__PREFIX_LEN] = "";
     H5AC_aux_t * aux_ptr = NULL;
 #endif /* H5_HAVE_PARALLEL */
+    struct H5C_cache_image_ctl_t int_ci_config = H5C__DEFAULT_CACHE_IMAGE_CTL;
     herr_t ret_value = SUCCEED;      /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
@@ -384,11 +386,16 @@ H5AC_create(const H5F_t *f, H5AC_cache_config_t *config_ptr)
     HDassert(f);
     HDassert(NULL == f->shared->cache);
     HDassert(config_ptr != NULL) ;
+    HDassert(image_config_ptr != NULL) ;
+    HDassert(image_config_ptr->version == H5AC__CURR_CACHE_IMAGE_CONFIG_VERSION);
     HDcompile_assert(NELMTS(H5AC_class_s) == H5AC_NTYPES);
     HDcompile_assert(H5C__MAX_NUM_TYPE_IDS == H5AC_NTYPES);
 
+    /* Validate configurations */
     if(H5AC_validate_config(config_ptr) < 0)
         HGOTO_ERROR(H5E_CACHE, H5E_BADVALUE, FAIL, "Bad cache configuration")
+    if(H5AC_validate_cache_image_config(image_config_ptr) < 0)
+        HGOTO_ERROR(H5E_CACHE, H5E_BADVALUE, FAIL, "Bad cache image configuration")
 
 #ifdef H5_HAVE_PARALLEL
     if(H5F_HAS_FEATURE(f, H5FD_FEAT_HAS_MPI)) {
@@ -430,6 +437,7 @@ H5AC_create(const H5F_t *f, H5AC_cache_config_t *config_ptr)
         aux_ptr->candidate_slist_ptr = NULL;
         aux_ptr->write_done = NULL;
         aux_ptr->sync_point_done = NULL;
+        aux_ptr->p0_image_len = 0;
 
         sprintf(prefix, "%d:", mpi_rank);
 
@@ -504,6 +512,20 @@ H5AC_create(const H5F_t *f, H5AC_cache_config_t *config_ptr)
     if(H5AC_set_cache_auto_resize_config(f->shared->cache, config_ptr) < 0)
         HGOTO_ERROR(H5E_CACHE, H5E_CANTALLOC, FAIL, "auto resize configuration failed")
 
+    /* don't need to get the current H5C image config here since the
+     * cache has just been created, and thus f->shared->cache->image_ctl 
+     * must still set to its initial value (H5C__DEFAULT_CACHE_IMAGE_CTL).  
+     * Note that this not true as soon as control returns to the application
+     * program, as some test code modifies f->shared->cache->image_ctl.
+     */
+    int_ci_config.version            = image_config_ptr->version;
+    int_ci_config.generate_image     = image_config_ptr->generate_image;
+    int_ci_config.save_resize_status = image_config_ptr->save_resize_status;
+    int_ci_config.entry_ageout       = image_config_ptr->entry_ageout;
+
+    if(H5C_set_cache_image_config(f, f->shared->cache, &int_ci_config) < 0)
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTALLOC, FAIL, "auto resize configuration failed")
+
 done:
 #ifdef H5_HAVE_PARALLEL
     /* if there is a failure, try to tidy up the auxilary structure */
@@ -982,6 +1004,41 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5AC_load_cache_image_on_next_protect
+ *
+ * Purpose:     Load the cache image block at the specified location,
+ *              decode it, and insert its contents into the metadata
+ *              cache.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ * Programmer:  John Mainzer
+ *              7/6/15
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5AC_load_cache_image_on_next_protect(H5F_t * f, haddr_t addr, hsize_t len,
+    hbool_t rw)
+{
+    herr_t              ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Sanity checks */
+    HDassert(f);
+    HDassert(f->shared);
+    HDassert(f->shared->cache);
+
+    if(H5C_load_cache_image_on_next_protect(f, addr, len, rw) < 0)
+        HGOTO_ERROR(H5E_CACHE, H5E_CANTLOAD, FAIL, "call to H5C_load_cache_image_on_next_protect failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5AC_load_cache_image_on_next_protect() */
+
+
+/*-------------------------------------------------------------------------
  * Function:    H5AC_mark_entry_dirty
  *
  * Purpose:	Mark a pinned or protected entry as dirty.  The target
@@ -2395,6 +2452,61 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5AC_validate_cache_image_config()
+ *
+ * Purpose:     Run a sanity check on the contents of the supplied
+ *		instance of H5AC_cache_image_config_t.
+ *
+ *              Do nothing and return SUCCEED if no errors are detected,
+ *              and flag an error and return FAIL otherwise.
+ *
+ *		At present, this function operates by packing the data
+ *		from the instance of H5AC_cache_image_config_t into an 
+ *		instance of H5C_cache_image_ctl_t, and then calling
+ *		H5C_validate_cache_image_config().  If and when 
+ *              H5AC_cache_image_config_t and H5C_cache_image_ctl_t 
+ *		diverge, we may have to change this.
+ *
+ * Return:      Non-negative on success/Negative on failure
+ *
+ * Programmer:  John Mainzer
+ *              6/25/15
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5AC_validate_cache_image_config(H5AC_cache_image_config_t *config_ptr)
+{
+    H5C_cache_image_ctl_t internal_config = H5C__DEFAULT_CACHE_IMAGE_CTL;
+    herr_t              ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Check args */
+    if(config_ptr == NULL)
+        HGOTO_ERROR(H5E_CACHE, H5E_BADVALUE, FAIL, "NULL config_ptr on entry")
+
+    if(config_ptr->version != H5AC__CURR_CACHE_IMAGE_CONFIG_VERSION)
+        HGOTO_ERROR(H5E_CACHE, H5E_BADVALUE, FAIL, "Unknown image config version")
+
+    /* don't need to get the current H5C image config here since the
+     * default values of fields not in the H5AC config will always be 
+     * valid.
+     */
+    internal_config.version            = config_ptr->version;
+    internal_config.generate_image     = config_ptr->generate_image;
+    internal_config.save_resize_status = config_ptr->save_resize_status;
+    internal_config.entry_ageout       = config_ptr->entry_ageout;
+
+    if(H5C_validate_cache_image_config(&internal_config) < 0)
+        HGOTO_ERROR(H5E_CACHE, H5E_BADVALUE, FAIL, "error(s) in new cache image config")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5AC_validate_cache_image_config() */
+
+
+/*-------------------------------------------------------------------------
  *
  * Function:    H5AC__check_if_write_permitted
  *
diff --git a/src/H5ACdbg.c b/src/H5ACdbg.c
index 8d99c6f..e2f7b13 100644
--- a/src/H5ACdbg.c
+++ b/src/H5ACdbg.c
@@ -252,6 +252,207 @@ done:
 
 /*-------------------------------------------------------------------------
  *
+ * Function:    H5AC_get_entry_ptr_from_addr()
+ *
+ * Purpose:     Debugging function that attempts to look up an entry in the
+ *              cache by its file address, and if found, returns a pointer
+ *              to the entry in *entry_ptr_ptr.  If the entry is not in the
+ *              cache, *entry_ptr_ptr is set to NULL.
+ *
+ *              WARNING: This call should be used only in debugging
+ *                       routines, and it should be avoided when
+ *                       possible.
+ *
+ *                       Further, if we ever multi-thread the cache,
+ *                       this routine will have to be either discarded
+ *                       or heavily re-worked.
+ *
+ *                       Finally, keep in mind that the entry whose
+ *                       pointer is obtained in this fashion may not
+ *                       be in a stable state.
+ *
+ *              Note that this function is only defined if NDEBUG
+ *              is not defined.
+ *
+ *              As heavy use of this function is almost certainly a
+ *              bad idea, the metadata cache tracks the number of
+ *              successful calls to this function, and (if
+ *              H5C_DO_SANITY_CHECKS is defined) displays any
+ *              non-zero count on cache shutdown.
+ *
+ *              This function is just a wrapper that calls the H5C
+ *              version of the function.
+ *
+ * Return:      FAIL if error is detected, SUCCEED otherwise.
+ *
+ * Programmer:  John Mainzer, 5/30/14
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+herr_t
+H5AC_get_entry_ptr_from_addr(const H5F_t *f, haddr_t addr, void **entry_ptr_ptr)
+{
+    H5C_t *cache_ptr;               /* Ptr to cache */
+    herr_t ret_value = SUCCEED;     /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Sanity checks */
+    HDassert(f);
+    HDassert(f->shared);
+    cache_ptr = f->shared->cache;
+
+    if(H5C_get_entry_ptr_from_addr(cache_ptr, addr, entry_ptr_ptr) < 0)
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "H5C_get_entry_ptr_from_addr() failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5AC_get_entry_ptr_from_addr() */
+#endif /* NDEBUG */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5AC_flush_dependency_exists()
+ *
+ * Purpose:     Test to see if a flush dependency relationship exists
+ *              between the supplied parent and child.  Both parties
+ *              are indicated by addresses so as to avoid the necessity
+ *              of protect / unprotect calls prior to this call.
+ *
+ *              If either the parent or the child is not in the metadata
+ *              cache, the function sets *fd_exists_ptr to FALSE.
+ *
+ *              If both are in the cache, the childs list of parents is
+ *              searched for the proposed parent.  If the proposed parent
+ *              is found in the childs parent list, the function sets
+ *              *fd_exists_ptr to TRUE.  In all other non-error cases,
+ *              the function sets *fd_exists_ptr FALSE.
+ *
+ * Return:      SUCCEED on success/FAIL on failure.  Note that
+ *              *fd_exists_ptr is undefined on failure.
+ *
+ * Programmer:  John Mainzer
+ *              9/28/16
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+herr_t
+H5AC_flush_dependency_exists(H5F_t *f, haddr_t parent_addr, haddr_t child_addr,
+    hbool_t *fd_exists_ptr)
+{
+    H5C_t *cache_ptr;               /* Ptr to cache */
+    herr_t  ret_value = FAIL;       /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    /* Sanity checks */
+    HDassert(f);
+    HDassert(f->shared);
+    cache_ptr = f->shared->cache;
+
+    ret_value = H5C_flush_dependency_exists(cache_ptr, parent_addr, child_addr, fd_exists_ptr);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5AC_flush_dependency_exists() */
+#endif /* NDEBUG */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function:    H5AC_verify_entry_type()
+ *
+ * Purpose:     Debugging function that attempts to look up an entry in the
+ *              cache by its file address, and if found, test to see if its
+ *              type field contains the expected value.
+ *
+ *              If the specified entry is in cache, *in_cache_ptr is set
+ *              to TRUE, and *type_ok_ptr is set to TRUE or FALSE depending 
+ *		on whether the entries type field matches the 
+ *		expected_type parameter
+ *
+ *              If the target entry is not in cache, *in_cache_ptr is
+ *              set to FALSE, and *type_ok_ptr is undefined.
+ *
+ *              Note that this function is only defined if NDEBUG
+ *              is not defined.
+ *
+ *              This function is just a wrapper that calls the H5C
+ *              version of the function.
+ *
+ * Return:      FAIL if error is detected, SUCCEED otherwise.
+ *
+ * Programmer:  John Mainzer, 5/30/14
+ *
+ * Changes:	None.
+ *
+ *						JRM -- 9/17/16
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+herr_t
+H5AC_verify_entry_type(const H5F_t *f, haddr_t addr, 
+    const H5AC_class_t *expected_type, hbool_t *in_cache_ptr, 
+    hbool_t *type_ok_ptr)
+{
+    H5C_t             * cache_ptr;
+    herr_t              ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Sanity checks */
+    HDassert(f);
+    HDassert(f->shared);
+    cache_ptr = f->shared->cache;
+
+    if(H5C_verify_entry_type(cache_ptr, addr, expected_type, in_cache_ptr, type_ok_ptr) < 0)
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "H5C_verify_entry_type() failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5AC_verify_entry_type() */
+#endif /* NDEBUG */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5AC_get_serialization_in_progress
+ *
+ * Purpose:     Return the current value of 
+ *              cache_ptr->serialization_in_progress.
+ *
+ * Return:      Current value of cache_ptr->serialization_in_progress.
+ *
+ * Programmer:  John Mainzer
+ *              8/24/15
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+hbool_t
+H5AC_get_serialization_in_progress(H5F_t *f)
+{
+    H5C_t * cache_ptr;
+    hbool_t ret_value = FALSE;      /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    /* Sanity check */
+    HDassert(f);
+    HDassert(f->shared);
+    cache_ptr = f->shared->cache;
+
+    /* Set return value */
+    ret_value = H5C_get_serialization_in_progress(cache_ptr);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5AC_get_serialization_in_progress() */
+#endif /* NDEBUG */
+
+
+/*-------------------------------------------------------------------------
+ *
  * Function:    H5AC_cache_is_clean()
  *
  * Purpose:     Debugging function that verifies that all rings in the
diff --git a/src/H5ACpkg.h b/src/H5ACpkg.h
index dbbd8a0..816f1d5 100644
--- a/src/H5ACpkg.h
+++ b/src/H5ACpkg.h
@@ -351,6 +351,12 @@ H5FL_EXTERN(H5AC_aux_t);
  *		this verification.  The field is set to NULL when the 
  *		callback is not needed.
  *
+ * The following field supports the metadata cache image feature.
+ *
+ * p0_image_len: unsiged integer containing the length of the metadata cache
+ *		image constructed by MPI process 0.  This field should be 0
+ *		if the value is unknown, or if cache image is not enabled.
+ *
  ****************************************************************************/
 
 #ifdef H5_HAVE_PARALLEL
@@ -400,6 +406,9 @@ typedef struct H5AC_aux_t
 
     void	(* sync_point_done)(int num_writes, 
                                     haddr_t * written_entries_tbl);
+
+    unsigned    p0_image_len;
+
 } H5AC_aux_t; /* struct H5AC_aux_t */
 #endif /* H5_HAVE_PARALLEL */
 
diff --git a/src/H5ACprivate.h b/src/H5ACprivate.h
index 683be2b..9f28b18 100644
--- a/src/H5ACprivate.h
+++ b/src/H5ACprivate.h
@@ -88,6 +88,7 @@ typedef enum {
     H5AC_DRVRINFO_ID,           /* (26) driver info block (supplements superblock)  */
     H5AC_EPOCH_MARKER_ID,       /* (27) epoch marker - always internal to cache     */
     H5AC_PROXY_ENTRY_ID,        /* (28) cache entry proxy                           */
+    H5AC_PREFETCHED_ENTRY_ID, 	/* (29) prefetched entry - always internal to cache */
     H5AC_NTYPES                 /* Number of types, must be last                    */
 } H5AC_type_t;
 
@@ -110,14 +111,22 @@ typedef enum {
  *	 use the dump_stats parameter to takedown_cache(), or call 
  *	 H5C_stats() directly.
  *					JRM -- 4/12/15
+ *
+ * Added the H5AC_DUMP_IMAGE_STATS_ON_CLOSE #define, which works much 
+ * the same way as H5AC_DUMP_STATS_ON_CLOSE.  However, the set of stats
+ * displayed is much smaller, and directed purely at the cache image feature.
+ *
+ *					JRM -- 11/1/15
  */
 #if H5C_COLLECT_CACHE_STATS
 
 #define H5AC_DUMP_STATS_ON_CLOSE	0
+#define H5AC_DUMP_IMAGE_STATS_ON_CLOSE  0
 
 #else /* H5C_COLLECT_CACHE_STATS */
 
 #define H5AC_DUMP_STATS_ON_CLOSE	0
+#define H5AC_DUMP_IMAGE_STATS_ON_CLOSE  0
 
 #endif /* H5C_COLLECT_CACHE_STATS */
 
@@ -318,7 +327,13 @@ H5_DLLVAR hid_t H5AC_rawdata_dxpl_id;
 }
 #endif /* H5_HAVE_PARALLEL */
 
-
+#define H5AC__DEFAULT_CACHE_IMAGE_CONFIG                                     \
+{                                                                            \
+   /* int32_t version            = */ H5AC__CURR_CACHE_IMAGE_CONFIG_VERSION, \
+   /* hbool_t generate_image     = */ FALSE,                                 \
+   /* hbool_t save_resize_status = */ FALSE,                                 \
+   /* int32_t entry_ageout       = */ H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE  \
+}
 /*
  * Library prototypes.
  */
@@ -388,12 +403,14 @@ H5_DLLVAR const H5AC_class_t H5AC_SUPERBLOCK[1];
 H5_DLLVAR const H5AC_class_t H5AC_DRVRINFO[1];
 H5_DLLVAR const H5AC_class_t H5AC_EPOCH_MARKER[1];
 H5_DLLVAR const H5AC_class_t H5AC_PROXY_ENTRY[1];
+H5_DLLVAR const H5AC_class_t H5AC_PREFETCHED_ENTRY[1];
 
 
 /* external function declarations: */
 
 H5_DLL herr_t H5AC_init(void);
-H5_DLL herr_t H5AC_create(const H5F_t *f, H5AC_cache_config_t *config_ptr);
+H5_DLL herr_t H5AC_create(const H5F_t *f, H5AC_cache_config_t *config_ptr,
+    H5AC_cache_image_config_t * image_config_ptr);
 H5_DLL herr_t H5AC_get_entry_status(const H5F_t *f, haddr_t addr,
     unsigned *status_ptr);
 H5_DLL herr_t H5AC_insert_entry(H5F_t *f, hid_t dxpl_id, const H5AC_class_t *type,
@@ -430,6 +447,11 @@ H5_DLL herr_t H5AC_set_cache_auto_resize_config(H5AC_t *cache_ptr,
     H5AC_cache_config_t *config_ptr);
 H5_DLL herr_t H5AC_validate_config(H5AC_cache_config_t *config_ptr);
 
+/* Cache image routines */
+H5_DLL herr_t H5AC_load_cache_image_on_next_protect(H5F_t *f, haddr_t addr, 
+    hsize_t len, hbool_t rw);
+H5_DLL herr_t H5AC_validate_cache_image_config(H5AC_cache_image_config_t *config_ptr);
+
 /* Tag & Ring routines */
 H5_DLL herr_t H5AC_tag(hid_t dxpl_id, haddr_t metadata_tag, haddr_t *prev_tag);
 H5_DLL herr_t H5AC_flush_tagged_metadata(H5F_t * f, haddr_t metadata_tag, hid_t dxpl_id);
@@ -462,6 +484,14 @@ H5_DLL herr_t H5AC_add_candidate(H5AC_t * cache_ptr, haddr_t addr);
 H5_DLL herr_t H5AC_stats(const H5F_t *f);
 H5_DLL herr_t H5AC_dump_cache(const H5F_t *f);
 #ifndef NDEBUG
+H5_DLL herr_t H5AC_get_entry_ptr_from_addr(const H5F_t *f, haddr_t addr,
+    void **entry_ptr_ptr);
+H5_DLL herr_t H5AC_flush_dependency_exists(H5F_t *f, haddr_t parent_addr, 
+    haddr_t child_addr, hbool_t *fd_exists_ptr);
+H5_DLL herr_t H5AC_verify_entry_type(const H5F_t *f, haddr_t addr,
+    const H5AC_class_t *expected_type, hbool_t *in_cache_ptr,
+    hbool_t *type_ok_ptr);
+H5_DLL hbool_t H5AC_get_serialization_in_progress(H5F_t *f);
 H5_DLL hbool_t H5AC_cache_is_clean(const H5F_t *f, H5AC_ring_t inner_ring);
 #endif /* NDEBUG */ /* end debugging functions */
 
diff --git a/src/H5ACpublic.h b/src/H5ACpublic.h
index dd16764..5fdb3f4 100644
--- a/src/H5ACpublic.h
+++ b/src/H5ACpublic.h
@@ -508,6 +508,67 @@ typedef struct H5AC_cache_config_t
 } H5AC_cache_config_t;
 
 
+/****************************************************************************
+ *
+ * structure H5AC_cache_image_config_t
+ *
+ * H5AC_cache_image_ctl_t is a public structure intended for use in public 
+ * APIs.  At least in its initial incarnation, it is a copy of struct
+ * H5C_cache_image_ctl_t.
+ *
+ * The fields of the structure are discussed individually below:
+ *
+ * version: Integer field containing the version number of this version
+ *      of the H5C_image_ctl_t structure.  Any instance of
+ *      H5C_image_ctl_t passed to the cache must have a known
+ *      version number, or an error will be flagged.
+ *
+ * generate_image:  Boolean flag indicating whether a cache image should
+ *      be created on file close.
+ *
+ * save_resize_status:	Boolean flag indicating whether the cache image 
+ *	should include the adaptive cache resize configuration and status.
+ *	Note that this field is ignored at present.
+ *
+ * entry_ageout:	Integer field indicating the maximum number of 
+ *	times a prefetched entry can appear in subsequent cache images.
+ *	This field exists to allow the user to avoid the buildup of 
+ *	infrequently used entries in long sequences of cache images.
+ *
+ *	The value of this field must lie in the range
+ *	H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE (-1) to 
+ *	H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX (100).
+ *
+ *	H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE means that no limit 
+ *	is imposed on number of times a prefeteched entry can appear
+ *	in subsequent cache images.
+ *
+ *	A value of 0 prevents prefetched entries from being included 
+ *	in cache images.
+ *
+ *	Positive integers restrict prefetched entries to the specified
+ *	number of appearances.
+ *
+ *	Note that the number of subsequent cache images that a prefetched
+ *	entry has appeared in is tracked in an 8 bit field.  Thus, while
+ *	H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX can be increased from its 
+ *	current value, any value in excess of 255 will be the functional 
+ *	equivalent of H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE.
+ *
+ ****************************************************************************/
+
+#define H5AC__CURR_CACHE_IMAGE_CONFIG_VERSION 	1
+
+#define H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE	-1
+#define H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX	100
+
+typedef struct H5AC_cache_image_config_t {
+    int32_t                             version;
+    hbool_t                             generate_image;
+    hbool_t                             save_resize_status;
+    int32_t                             entry_ageout;
+} H5AC_cache_image_config_t;
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/H5C.c b/src/H5C.c
index 2d1dc4d..73806ad 100644
--- a/src/H5C.c
+++ b/src/H5C.c
@@ -46,9 +46,9 @@
  *	 - Change protect/unprotect to lock/unlock.
  *
  *	 - Flush entries in increasing address order in
- *	   H5C_make_space_in_cache().
+ *	   H5C__make_space_in_cache().
  *
- *	 - Also in H5C_make_space_in_cache(), use high and low water marks
+ *	 - Also in H5C__make_space_in_cache(), use high and low water marks
  *	   to reduce the number of I/O calls.
  *
  *	 - When flushing, attempt to combine contiguous entries to reduce
@@ -155,11 +155,6 @@ static void * H5C_load_entry(H5F_t *             f,
                              haddr_t             addr,
                              void *              udata);
 
-static herr_t H5C_make_space_in_cache(H5F_t * f,
-                                      hid_t   dxpl_id,
-       	                              size_t  space_needed,
-                                      hbool_t write_permitted);
-
 static herr_t H5C__mark_flush_dep_dirty(H5C_cache_entry_t * entry);
 
 static herr_t H5C__mark_flush_dep_clean(H5C_cache_entry_t * entry);
@@ -389,6 +384,7 @@ H5C_create(size_t		      max_cache_size,
     cache_ptr->resize_enabled			= FALSE;
     cache_ptr->cache_full			= FALSE;
     cache_ptr->size_decreased			= FALSE;
+    cache_ptr->resize_in_progress		= FALSE;
 
     (cache_ptr->resize_ctl).version		= H5C__CURR_AUTO_SIZE_CTL_VER;
     (cache_ptr->resize_ctl).rpt_fcn		= NULL;
@@ -437,9 +433,32 @@ H5C_create(size_t		      max_cache_size,
         ((cache_ptr->epoch_markers)[i]).type		 = H5AC_EPOCH_MARKER;
     }
 
+    /* Initialize cache image generation on file close related fields.
+     * Initial value of image_ctl must match H5C__DEFAULT_CACHE_IMAGE_CTL
+     * in H5Cprivate.h.
+     */
+    cache_ptr->image_ctl.version            = H5C__CURR_CACHE_IMAGE_CTL_VER;
+    cache_ptr->image_ctl.generate_image     = FALSE;
+    cache_ptr->image_ctl.save_resize_status = FALSE;
+    cache_ptr->image_ctl.entry_ageout       = -1;
+    cache_ptr->image_ctl.flags              = H5C_CI__ALL_FLAGS;
+
+    cache_ptr->serialization_in_progress= FALSE;
+    cache_ptr->load_image		= FALSE;
+    cache_ptr->image_loaded             = FALSE;
+    cache_ptr->delete_image		= FALSE;
+    cache_ptr->image_addr		= HADDR_UNDEF;
+    cache_ptr->image_len		= 0;
+    cache_ptr->image_data_len		= 0;
+
     cache_ptr->entries_loaded_counter		= 0;
     cache_ptr->entries_inserted_counter		= 0;
     cache_ptr->entries_relocated_counter	= 0;
+    cache_ptr->entry_fd_height_change_counter	= 0;
+
+    cache_ptr->num_entries_in_image	= 0;
+    cache_ptr->image_entries		= NULL;
+    cache_ptr->image_buffer		= NULL;
 
     /* initialize free space manager related fields: */
     cache_ptr->rdfsm_settled		= FALSE;
@@ -456,6 +475,10 @@ H5C_create(size_t		      max_cache_size,
 
     cache_ptr->prefix[0]			= '\0';  /* empty string */
 
+#ifndef NDEBUG
+    cache_ptr->get_entry_ptr_from_addr_counter  = 0;
+#endif /* NDEBUG */
+
     /* Set return value */
     ret_value = cache_ptr;
 
@@ -733,6 +756,21 @@ H5C_prep_for_file_close(H5F_t *f, hid_t dxpl_id)
     /* Make certain there aren't any protected entries */
     HDassert(cache_ptr->pl_len == 0);
 
+    /* If the file is opened and closed without any access to 
+     * any group or dataset, it is possible that the cache image (if 
+     * it exists) has not been read yet.  Do this now if required.
+     */
+    if(cache_ptr->load_image) {
+        cache_ptr->load_image = FALSE;
+        if(H5C__load_cache_image(f, dxpl_id) < 0)
+	    HGOTO_ERROR(H5E_CACHE, H5E_CANTLOAD, FAIL, "Can't load cache image")
+    } /* end if */
+
+    /* Generate the cache image, if requested */
+    if(cache_ptr->image_ctl.generate_image)
+        if(H5C__prep_image_for_file_close(f, dxpl_id) < 0)
+	    HGOTO_ERROR(H5E_CACHE, H5E_CANTCREATE, FAIL, "Can't create cache image")
+
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* H5C_prep_for_file_close() */
@@ -775,10 +813,20 @@ H5C_dest(H5F_t * f, hid_t dxpl_id)
     HDassert(cache_ptr->magic == H5C__H5C_T_MAGIC);
     HDassert(cache_ptr->close_warning_received);
 
+#if H5AC_DUMP_IMAGE_STATS_ON_CLOSE
+    if(H5C_image_stats(cache_ptr, TRUE) < 0)
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Can't display cache image stats")
+#endif /* H5AC_DUMP_IMAGE_STATS_ON_CLOSE */
+
     /* Flush and invalidate all cache entries */
     if(H5C_flush_invalidate_cache(f, dxpl_id, H5C__NO_FLAGS_SET) < 0 )
         HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush cache")
 
+    /* Generate & write cache image if requested */
+    if(cache_ptr->image_ctl.generate_image)
+        if(H5C__generate_cache_image(f, dxpl_id, cache_ptr) < 0)
+            HGOTO_ERROR(H5E_CACHE, H5E_CANTCREATE, FAIL, "Can't generate metadata cache image")
+
     if(cache_ptr->slist_ptr != NULL) {
         H5SL_close(cache_ptr->slist_ptr);
         cache_ptr->slist_ptr = NULL;
@@ -790,6 +838,12 @@ H5C_dest(H5F_t * f, hid_t dxpl_id)
     } /* end if */
 
 #ifndef NDEBUG
+#if H5C_DO_SANITY_CHECKS
+    if(cache_ptr->get_entry_ptr_from_addr_counter > 0)
+        HDfprintf(stdout, "*** %ld calls to H5C_get_entry_ptr_from_add(). ***\n",
+                cache_ptr->get_entry_ptr_from_addr_counter);
+#endif /* H5C_DO_SANITY_CHECKS */
+
     cache_ptr->magic = 0;
 #endif /* NDEBUG */
 
@@ -1173,7 +1227,7 @@ H5C_flush_to_min_clean(H5F_t * f,
                     "cache write is not permitted!?!\n");
     }
 #if 1 /* original code */
-    if(H5C_make_space_in_cache(f, dxpl_id, (size_t)0, write_permitted) < 0)
+    if(H5C__make_space_in_cache(f, dxpl_id, (size_t)0, write_permitted) < 0)
         HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "H5C__make_space_in_cache failed")
 #else /* modified code -- commented out for now */
     if ( cache_ptr->max_cache_size > cache_ptr->index_size ) {
@@ -1343,6 +1397,7 @@ H5C_insert_entry(H5F_t *             f,
     HDassert( cache_ptr );
     HDassert( cache_ptr->magic == H5C__H5C_T_MAGIC );
     HDassert( type );
+    HDassert( type->mem_type == cache_ptr->class_table_ptr[type->id]->mem_type );
     HDassert( type->image_len );
     HDassert( H5F_addr_defined(addr) );
     HDassert( thing );
@@ -1442,6 +1497,22 @@ H5C_insert_entry(H5F_t *             f,
     entry_ptr->aux_next = NULL;
     entry_ptr->aux_prev = NULL;
 
+    /* initialize cache image related fields */
+    entry_ptr->include_in_image 		= FALSE;
+    entry_ptr->lru_rank         		= 0;
+    entry_ptr->image_dirty			= FALSE;
+    entry_ptr->fd_parent_count			= 0;
+    entry_ptr->fd_parent_addrs			= NULL;
+    entry_ptr->fd_child_count			= 0;
+    entry_ptr->fd_dirty_child_count		= 0;
+    entry_ptr->image_fd_height			= 0;
+    entry_ptr->prefetched			= FALSE;
+    entry_ptr->prefetch_type_id			= 0;
+    entry_ptr->age				= 0;
+#ifndef NDEBUG  /* debugging field */
+    entry_ptr->serialization_count		= 0;
+#endif /* NDEBUG */
+
 #ifdef H5_HAVE_PARALLEL
     entry_ptr->coll_next = NULL;
     entry_ptr->coll_prev = NULL;
@@ -1487,7 +1558,7 @@ H5C_insert_entry(H5F_t *             f,
 
         /* Note that space_needed is just the amount of space that
          * needed to insert the new entry without exceeding the cache
-         * size limit.  The subsequent call to H5C_make_space_in_cache()
+         * size limit.  The subsequent call to H5C__make_space_in_cache()
          * may evict the entries required to free more or less space
          * depending on conditions.  It MAY be less if the cache is
          * currently undersized, or more if the cache is oversized.
@@ -1510,8 +1581,8 @@ H5C_insert_entry(H5F_t *             f,
          * no point in worrying about the third.
          */
 
-        if(H5C_make_space_in_cache(f, dxpl_id, space_needed, write_permitted) < 0)
-            HGOTO_ERROR(H5E_CACHE, H5E_CANTINS, FAIL, "H5C_make_space_in_cache failed.")
+        if(H5C__make_space_in_cache(f, dxpl_id, space_needed, write_permitted) < 0)
+            HGOTO_ERROR(H5E_CACHE, H5E_CANTINS, FAIL, "H5C__make_space_in_cache failed.")
     }
 
     H5C__INSERT_IN_INDEX(cache_ptr, entry_ptr, FAIL)
@@ -2342,6 +2413,7 @@ H5C_protect(H5F_t *		f,
     HDassert( cache_ptr );
     HDassert( cache_ptr->magic == H5C__H5C_T_MAGIC );
     HDassert( type );
+    HDassert( type->mem_type == cache_ptr->class_table_ptr[type->id]->mem_type );
     HDassert( H5F_addr_defined(addr) );
 
 #if H5C_DO_EXTREME_SANITY_CHECKS
@@ -2351,6 +2423,13 @@ H5C_protect(H5F_t *		f,
         HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, NULL, "an extreme sanity check failed on entry")
 #endif /* H5C_DO_EXTREME_SANITY_CHECKS */
 
+    /* Load the cache image, if requested */
+    if(cache_ptr->load_image) {
+        cache_ptr->load_image = FALSE;
+        if(H5C__load_cache_image(f, dxpl_id) < 0)
+            HGOTO_ERROR(H5E_CACHE, H5E_CANTLOAD, NULL, "Can't load cache image")
+    } /* end if */
+
     read_only          = ( (flags & H5C__READ_ONLY_FLAG) != 0 );
     flush_last         = ( (flags & H5C__FLUSH_LAST_FLAG) != 0 );
 
@@ -2384,6 +2463,21 @@ H5C_protect(H5F_t *		f,
         if(entry_ptr->ring != ring)
             HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, NULL, "ring type mismatch occured for cache entry\n")
 
+        HDassert(entry_ptr->magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
+
+        if(entry_ptr->prefetched) {
+            /* This call removes the prefetched entry from the cache,
+             * and replaces it with an entry deserialized from the 
+             * image of the prefetched entry.
+             */
+            if(H5C__deserialize_prefetched_entry(f, dxpl_id, cache_ptr, &entry_ptr, type, addr, udata) < 0)
+                HGOTO_ERROR(H5E_CACHE, H5E_CANTLOAD, NULL, "can't deserialize prefetched entry.")
+
+            HDassert(entry_ptr->magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
+            HDassert(!entry_ptr->prefetched);
+            HDassert(entry_ptr->addr == addr);
+        } /* end if */
+
         /* Check for trying to load the wrong type of entry from an address */
         if(entry_ptr->type != type)
             HGOTO_ERROR(H5E_CACHE, H5E_BADTYPE, NULL, "incorrect cache entry type")
@@ -2501,7 +2595,7 @@ H5C_protect(H5F_t *		f,
            empty_space = cache_ptr->max_cache_size - cache_ptr->index_size;
 
 	/* try to free up if necceary and if evictions are permitted.  Note
-	 * that if evictions are enabled, we will call H5C_make_space_in_cache()
+	 * that if evictions are enabled, we will call H5C__make_space_in_cache()
 	 * regardless if the min_free_space requirement is not met.
 	 */
         if ( ( cache_ptr->evictions_enabled ) &&
@@ -2536,7 +2630,7 @@ H5C_protect(H5F_t *		f,
 
             /* Note that space_needed is just the amount of space that
              * needed to insert the new entry without exceeding the cache
-             * size limit.  The subsequent call to H5C_make_space_in_cache()
+             * size limit.  The subsequent call to H5C__make_space_in_cache()
              * may evict the entries required to free more or less space
              * depending on conditions.  It MAY be less if the cache is
              * currently undersized, or more if the cache is oversized.
@@ -2563,8 +2657,8 @@ H5C_protect(H5F_t *		f,
              * see no point in worrying about the fourth.
              */
 
-            if(H5C_make_space_in_cache(f, dxpl_id, space_needed, write_permitted) < 0 )
-                HGOTO_ERROR(H5E_CACHE, H5E_CANTPROTECT, NULL, "H5C_make_space_in_cache failed 1.")
+            if(H5C__make_space_in_cache(f, dxpl_id, space_needed, write_permitted) < 0 )
+                HGOTO_ERROR(H5E_CACHE, H5E_CANTPROTECT, NULL, "H5C__make_space_in_cache failed 1.")
         }
 
         /* Insert the entry in the hash table.  It can't be dirty yet, so
@@ -2684,7 +2778,7 @@ H5C_protect(H5F_t *		f,
              * bring the cache size down to the current maximum cache size.
 	     *
 	     * Also, if the min_clean_size requirement is not met, we
-	     * should also call H5C_make_space_in_cache() to bring us
+	     * should also call H5C__make_space_in_cache() to bring us
 	     * into complience.
              */
 
@@ -2701,8 +2795,8 @@ H5C_protect(H5F_t *		f,
 		if(cache_ptr->index_size > cache_ptr->max_cache_size)
                     cache_ptr->cache_full = TRUE;
 
-                if(H5C_make_space_in_cache(f, dxpl_id, (size_t)0, write_permitted) < 0 )
-                    HGOTO_ERROR(H5E_CACHE, H5E_CANTPROTECT, NULL, "H5C_make_space_in_cache failed 2.")
+                if(H5C__make_space_in_cache(f, dxpl_id, (size_t)0, write_permitted) < 0 )
+                    HGOTO_ERROR(H5E_CACHE, H5E_CANTPROTECT, NULL, "H5C__make_space_in_cache failed 2.")
             }
         }
     }
@@ -3815,6 +3909,7 @@ H5C_create_flush_dependency(void * parent_thing, void * child_thing)
                 HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for flush dependency parent list")
             child_entry->flush_dep_parent_nalloc *= 2;
         } /* end else */
+        cache_ptr->entry_fd_height_change_counter++;
     } /* end if */
 
     /* Add the dependency to the child's parent array */
@@ -4023,6 +4118,7 @@ H5C__auto_adjust_cache_size(H5F_t * f,
 {
     H5C_t *			cache_ptr = f->shared->cache;
     herr_t			result;
+    hbool_t			reentrant_call = FALSE;
     hbool_t			inserted_epoch_marker = FALSE;
     size_t			new_max_cache_size = 0;
     size_t			old_max_cache_size = 0;
@@ -4042,6 +4138,18 @@ H5C__auto_adjust_cache_size(H5F_t * f,
     HDassert( (double)0.0f <= (cache_ptr->resize_ctl).min_clean_fraction );
     HDassert( (cache_ptr->resize_ctl).min_clean_fraction <= (double)100.0f );
 
+    /* check to see if cache_ptr->resize_in_progress is TRUE.  If it, this
+     * is a re-entrant call via a client callback called in the resize 
+     * process.  To avoid an infinite recursion, set reentrant_call to 
+     * TRUE, and goto done.
+     */
+    if(cache_ptr->resize_in_progress) {
+        reentrant_call = TRUE;
+        HGOTO_DONE(SUCCEED);
+    } /* end if */
+
+    cache_ptr->resize_in_progress = TRUE;
+
     if ( !cache_ptr->resize_enabled ) {
 
         HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Auto cache resize disabled.")
@@ -4340,6 +4448,12 @@ H5C__auto_adjust_cache_size(H5F_t * f,
     }
 
 done:
+    /* Sanity checks */
+    HDassert(cache_ptr->resize_in_progress);
+    if(!reentrant_call)
+        cache_ptr->resize_in_progress = FALSE;
+    HDassert((!reentrant_call) || (cache_ptr->resize_in_progress));
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* H5C__auto_adjust_cache_size() */
 
@@ -6136,6 +6250,8 @@ H5C__flush_single_entry(H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_ptr,
     hbool_t		destroy_entry;		/* internal flag */
     hbool_t		generate_image;		/* internal flag */
     hbool_t		was_dirty;
+    hbool_t		suppress_image_entry_writes = FALSE;
+    hbool_t		suppress_image_entry_frees = FALSE;
     haddr_t             entry_addr = HADDR_UNDEF;
     herr_t		ret_value = SUCCEED;      /* Return value */
 
@@ -6178,6 +6294,28 @@ H5C__flush_single_entry(H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_ptr,
     else
         write_entry = FALSE;
 
+    /* if we have received close warning, and we have been instructed to 
+     * generate a metadata cache image, and we have actually constructed
+     * the entry images, set suppress_image_entry_frees to TRUE.
+     *
+     * Set suppress_image_entry_writes to TRUE if indicated by the 
+     * image_ctl flags.
+     */
+    if(cache_ptr->close_warning_received && cache_ptr->image_ctl.generate_image
+            && cache_ptr->num_entries_in_image > 0 && cache_ptr->image_entries) {
+        /* Sanity checks */
+        HDassert(entry_ptr->image_up_to_date || !(entry_ptr->include_in_image));
+        HDassert(entry_ptr->image_ptr || !(entry_ptr->include_in_image));
+        HDassert((!clear_only) || !(entry_ptr->include_in_image));
+        HDassert((!take_ownership) || !(entry_ptr->include_in_image));
+        HDassert((!free_file_space) || !(entry_ptr->include_in_image));
+
+        suppress_image_entry_frees = TRUE;
+
+        if(cache_ptr->image_ctl.flags & H5C_CI__SUPRESS_ENTRY_WRITES)
+            suppress_image_entry_writes = TRUE;
+    } /* end if */
+
     /* run initial sanity checks */
 #if H5C_DO_SANITY_CHECKS
     if(entry_ptr->in_slist) {
@@ -6232,6 +6370,9 @@ H5C__flush_single_entry(H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_ptr,
         } /* end if */
 
         if(!(entry_ptr->image_up_to_date)) {
+            /* Sanity check */
+            HDassert(!entry_ptr->prefetched);
+
             /* Generate the entry's image */
             if(H5C__generate_image(f, cache_ptr, entry_ptr, dxpl_id) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTGET, FAIL, "can't generate entry's image")
@@ -6252,7 +6393,17 @@ H5C__flush_single_entry(H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_ptr,
             HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Write when writes are always forbidden!?!?!")
 #endif /* H5C_DO_SANITY_CHECKS */
 
-        if(((entry_ptr->type->flags) & H5C__CLASS_SKIP_WRITES) == 0) {
+        /* Write the image to disk unless the write is suppressed.
+         *
+         * This happens if both suppress_image_entry_writes and 
+         * entry_ptr->include_in_image are TRUE, or if the 
+         * H5AC__CLASS_SKIP_WRITES is set in the entry's type.  This
+         * flag should only be used in test code
+         */
+        if((!suppress_image_entry_writes || !entry_ptr->include_in_image)
+                && (((entry_ptr->type->flags) & H5C__CLASS_SKIP_WRITES) == 0)) {
+            H5FD_mem_t mem_type = H5FD_MEM_DEFAULT;
+
 #ifdef H5_HAVE_PARALLEL
             if(cache_ptr->coll_write_list) {
                 if(H5SL_insert(cache_ptr->coll_write_list, entry_ptr, &entry_ptr->addr) < 0)
@@ -6260,7 +6411,15 @@ H5C__flush_single_entry(H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_ptr,
             } /* end if */
             else
 #endif /* H5_HAVE_PARALLEL */
-            if(H5F_block_write(f, entry_ptr->type->mem_type, entry_ptr->addr, entry_ptr->size, dxpl_id, entry_ptr->image_ptr) < 0)
+
+            if(entry_ptr->prefetched) {
+                HDassert(entry_ptr->type->id == H5AC_PREFETCHED_ENTRY_ID);
+                mem_type = cache_ptr->class_table_ptr[entry_ptr->prefetch_type_id]->mem_type;
+            } /* end if */
+            else
+                mem_type = entry_ptr->type->mem_type;
+
+            if(H5F_block_write(f, mem_type, entry_ptr->addr, entry_ptr->size, dxpl_id, entry_ptr->image_ptr) < 0)
                 HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "Can't write image to file.")
         } /* end if */
 
@@ -6405,10 +6564,29 @@ H5C__flush_single_entry(H5F_t *f, hid_t dxpl_id, H5C_cache_entry_t *entry_ptr,
         /* Sanity check */
         HDassert(0 == entry_ptr->flush_dep_nparents);
 
-        /* Start by freeing the buffer for the on disk image */
-        if(entry_ptr->image_ptr != NULL)
+        /* if both suppress_image_entry_frees and entry_ptr->include_in_image
+         * are true, simply set entry_ptr->image_ptr to NULL, as we have 
+         * another pointer to the buffer in an instance of H5C_image_entry_t
+         * in cache_ptr->image_entries.
+         *
+         * Otherwise, free the buffer if it exists.
+         */
+        if(suppress_image_entry_frees && entry_ptr->include_in_image) 
+            entry_ptr->image_ptr = NULL;
+        else if(entry_ptr->image_ptr != NULL)
             entry_ptr->image_ptr = H5MM_xfree(entry_ptr->image_ptr);
 
+        /* If the entry is not a prefetched entry, verify that the flush 
+         * dependency parents addresses array has been transfered.
+         *
+         * If the entry is prefetched, the free_isr routine will dispose of
+         * the flush dependency parents adresses array if necessary.
+         */
+        if(!entry_ptr->prefetched) {
+            HDassert(0 == entry_ptr->fd_parent_count);
+            HDassert(NULL == entry_ptr->fd_parent_addrs);
+        } /* end if */
+
         /* Check whether we should free the space in the file that 
          * the entry occupies 
          */
@@ -6884,6 +7062,22 @@ H5C_load_entry(H5F_t *              f,
     entry->coll_prev                    = NULL;
 #endif /* H5_HAVE_PARALLEL */
 
+    /* initialize cache image related fields */
+    entry->include_in_image             = FALSE;
+    entry->lru_rank                     = 0;
+    entry->image_dirty                  = FALSE;
+    entry->fd_parent_count              = 0;
+    entry->fd_parent_addrs              = NULL;
+    entry->fd_child_count               = 0;
+    entry->fd_dirty_child_count         = 0;
+    entry->image_fd_height              = 0;
+    entry->prefetched                   = FALSE;
+    entry->prefetch_type_id             = 0;
+    entry->age                          = 0;
+#ifndef NDEBUG  /* debugging field */
+    entry->serialization_count          = 0;
+#endif /* NDEBUG */
+
     H5C__RESET_CACHE_ENTRY_STATS(entry);
 
     ret_value = thing;
@@ -6904,7 +7098,7 @@ done:
 
 /*-------------------------------------------------------------------------
  *
- * Function:    H5C_make_space_in_cache
+ * Function:    H5C__make_space_in_cache
  *
  * Purpose:     Attempt to evict cache entries until the index_size
  *		is at least needed_space below max_cache_size.
@@ -6970,7 +7164,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5C_make_space_in_cache(H5F_t *f, hid_t dxpl_id, size_t space_needed,
+H5C__make_space_in_cache(H5F_t *f, hid_t dxpl_id, size_t space_needed,
     hbool_t	write_permitted)
 {
     H5C_t *		cache_ptr = f->shared->cache;
@@ -6990,7 +7184,7 @@ H5C_make_space_in_cache(H5F_t *f, hid_t dxpl_id, size_t space_needed,
     uint32_t 		num_corked_entries = 0;
     herr_t		ret_value = SUCCEED;      /* Return value */
 
-    FUNC_ENTER_NOAPI_NOINIT
+    FUNC_ENTER_PACKAGE
 
     /* Sanity checks */
     HDassert(f);
@@ -7260,7 +7454,7 @@ H5C_make_space_in_cache(H5F_t *f, hid_t dxpl_id, size_t space_needed,
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* H5C_make_space_in_cache() */
+} /* H5C__make_space_in_cache() */
 
 
 /*-------------------------------------------------------------------------
@@ -8083,6 +8277,10 @@ H5C__assert_flush_dep_nocycle(const H5C_cache_entry_t * entry,
  *              are about to delete the entry from the cache (i.e. on a 
  *              flush destroy).
  *
+ * Note:	This routine is very similar to H5C__serialize_single_entry
+ *		and changes to one should probably be reflected in the other.
+ *		Ideally, one should be eliminated.
+ *
  * Return:      Non-negative on success/Negative on failure
  *
  * Programmer:  Mohamad Chaarawi
@@ -8117,8 +8315,7 @@ H5C__generate_image(H5F_t *f, H5C_t *cache_ptr, H5C_cache_entry_t *entry_ptr,
     /* Check for any flags set in the pre-serialize callback */
     if(serialize_flags != H5C__SERIALIZE_NO_FLAGS_SET) {
         /* Check for unexpected flags from serialize callback */
-        if(serialize_flags & ~(H5C__SERIALIZE_RESIZED_FLAG | 
-                               H5C__SERIALIZE_MOVED_FLAG))
+        if(serialize_flags & ~(H5C__SERIALIZE_RESIZED_FLAG | H5C__SERIALIZE_MOVED_FLAG))
             HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unknown serialize flag(s)")
 
 #ifdef H5_HAVE_PARALLEL
@@ -8165,9 +8362,8 @@ H5C__generate_image(H5F_t *f, H5C_t *cache_ptr, H5C_cache_entry_t *entry_ptr,
             /* Update statistics for resizing the entry */
             H5C__UPDATE_STATS_FOR_ENTRY_SIZE_CHANGE(cache_ptr, entry_ptr, new_len);
 
-            /* update the hash table for the size change */
-            H5C__UPDATE_INDEX_FOR_SIZE_CHANGE(cache_ptr, entry_ptr->size, \
-                                              new_len, entry_ptr, !(entry_ptr->is_dirty));
+            /* Update the hash table for the size change */
+            H5C__UPDATE_INDEX_FOR_SIZE_CHANGE(cache_ptr, entry_ptr->size, new_len, entry_ptr, !(entry_ptr->is_dirty));
 
             /* The entry can't be protected since we are in the process of
              * flushing it.  Thus we must update the replacement policy data
@@ -8180,10 +8376,11 @@ H5C__generate_image(H5F_t *f, H5C_t *cache_ptr, H5C_cache_entry_t *entry_ptr,
              * for the flush or flush destroy yet, the entry should
              * be in the slist.  Thus update it for the size change.
              */
+            HDassert(entry_ptr->is_dirty);
             HDassert(entry_ptr->in_slist);
             H5C__UPDATE_SLIST_FOR_SIZE_CHANGE(cache_ptr, entry_ptr->size, new_len);
 
-            /* finally, update the entry for its new size */
+            /* Finally, update the entry for its new size */
             entry_ptr->size = new_len;
         } /* end if */
 
@@ -8200,10 +8397,10 @@ H5C__generate_image(H5F_t *f, H5C_t *cache_ptr, H5C_cache_entry_t *entry_ptr,
                 H5C__DELETE_FROM_INDEX(cache_ptr, entry_ptr, FAIL);
                 H5C__REMOVE_ENTRY_FROM_SLIST(cache_ptr, entry_ptr, FALSE);
 
-                /* update the entry for its new address */
+                /* Update the entry for its new address */
                 entry_ptr->addr = new_addr;
 
-                /* and then reinsert in the index and slist */
+                /* And then reinsert in the index and slist */
                 H5C__INSERT_IN_INDEX(cache_ptr, entry_ptr, FAIL);
                 H5C__INSERT_ENTRY_IN_SLIST(cache_ptr, entry_ptr, FAIL);
             } /* end if */
diff --git a/src/H5Cdbg.c b/src/H5Cdbg.c
index 7efba23..7f4c8e0 100644
--- a/src/H5Cdbg.c
+++ b/src/H5Cdbg.c
@@ -35,6 +35,7 @@
 /* Headers */
 /***********/
 #include "H5private.h"      /* Generic Functions            */
+#include "H5ACprivate.h"    /* Metadata Cache               */
 #include "H5Cpkg.h"         /* Cache                        */
 #include "H5Eprivate.h"     /* Error Handling               */
 
@@ -385,6 +386,7 @@ H5C_stats(H5C_t * cache_ptr,
     size_t      aggregate_max_size = 0;
     int32_t	aggregate_max_pins = 0;
     double      hit_rate;
+    double      prefetch_use_rate;
     double	average_successful_search_depth = 0.0f;
     double	average_failed_search_depth = 0.0f;
     double      average_entries_skipped_per_calls_to_msic = 0.0f;
@@ -648,6 +650,38 @@ H5C_stats(H5C_t * cache_ptr,
               (long long)(cache_ptr->LRU_scan_restarts),
               (long long)(cache_ptr->index_scan_restarts));
 
+    HDfprintf(stdout,
+	      "%s  cache image creations/loads/size   = %d / %d / %lld\n",
+              cache_ptr->prefix,
+              cache_ptr->images_created,
+              cache_ptr->images_loaded,
+              (long long)cache_ptr->last_image_size);
+
+    HDfprintf(stdout,
+	      "%s  prefetches / dirty prefetches      = %lld / %lld\n",
+              cache_ptr->prefix,
+              (long long)(cache_ptr->prefetches),
+              (long long)(cache_ptr->dirty_prefetches));
+
+    HDfprintf(stdout,
+	      "%s  prefetch hits/flushes/evictions    = %lld / %lld / %lld\n",
+              cache_ptr->prefix,
+              (long long)(cache_ptr->prefetch_hits),
+              (long long)(cache_ptr->flushes[H5AC_PREFETCHED_ENTRY_ID]),
+              (long long)(cache_ptr->evictions[H5AC_PREFETCHED_ENTRY_ID]));
+
+    if(cache_ptr->prefetches > 0)
+        prefetch_use_rate = 
+                   (double)100.0f * ((double)(cache_ptr->prefetch_hits)) /
+                   ((double)(cache_ptr->prefetches));
+    else
+        prefetch_use_rate = 0.0f;
+
+    HDfprintf(stdout,
+	      "%s  prefetched entry use rate          = %lf\n",
+              cache_ptr->prefix,
+              prefetch_use_rate);
+
 #if H5C_COLLECT_CACHE_ENTRY_STATS
 
     HDfprintf(stdout, "%s  aggregate max / min accesses       = %d / %d\n",
@@ -869,6 +903,14 @@ H5C_stats__reset(H5C_t H5_ATTR_UNUSED * cache_ptr)
     cache_ptr->LRU_scan_restarts		= 0;
     cache_ptr->index_scan_restarts              = 0;
 
+    cache_ptr->images_created           = 0;
+    cache_ptr->images_loaded            = 0;
+    cache_ptr->last_image_size          = (size_t)0;
+
+    cache_ptr->prefetches               = 0;
+    cache_ptr->dirty_prefetches			= 0;
+    cache_ptr->prefetch_hits			= 0;
+
 #if H5C_COLLECT_CACHE_ENTRY_STATS
     for(i = 0; i <= cache_ptr->max_type_id; i++) {
         cache_ptr->max_accesses[i]		= 0;
@@ -952,6 +994,303 @@ H5C__dump_entry(H5C_t *cache_ptr, const H5C_cache_entry_t *entry_ptr,
     if(entry_ptr->flush_dep_nchildren)
         H5C__dump_children(cache_ptr, entry_ptr, FALSE, "Child", indent);
 } /* end H5C__dump_entry() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C_flush_dependency_exists()
+ *
+ * Purpose:	Test to see if a flush dependency relationship exists 
+ *          between the supplied parent and child.  Both parties 
+ *          are indicated by addresses so as to avoid the necessity
+ *          of protect / unprotect calls prior to this call. 
+ *
+ *          If either the parent or the child is not in the metadata 
+ *          cache, the function sets *fd_exists_ptr to FALSE.
+ *
+ *          If both are in the cache, the childs list of parents is 
+ *          searched for the proposed parent.  If the proposed parent
+ *          is found in the childs parent list, the function sets
+ *          *fd_exists_ptr to TRUE.  In all other non-error cases, 
+ *          the function sets *fd_exists_ptr FALSE.
+ *
+ * Return:      SUCCEED on success/FAIL on failure.  Note that 
+ *              *fd_exists_ptr is undefined on failure.
+ *
+ * Programmer:  John Mainzer
+ *              9/28/16
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+herr_t
+H5C_flush_dependency_exists(H5C_t *cache_ptr, haddr_t parent_addr, haddr_t child_addr,
+    hbool_t *fd_exists_ptr)
+{
+    hbool_t             fd_exists = FALSE;  /* whether flush dependency exists */
+    H5C_cache_entry_t *	parent_ptr;         /* Ptr to parent entry */
+    H5C_cache_entry_t *	child_ptr;          /* Ptr to child entry */
+    hbool_t             ret_value = FALSE;  /* Return value */
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    /* Sanity checks */
+    HDassert(cache_ptr);
+    HDassert(cache_ptr->magic == H5C__H5C_T_MAGIC);
+    HDassert(H5F_addr_defined(parent_addr));
+    HDassert(H5F_addr_defined(child_addr));
+    HDassert(fd_exists_ptr);
+
+    H5C__SEARCH_INDEX(cache_ptr, parent_addr, parent_ptr, FAIL)
+    H5C__SEARCH_INDEX(cache_ptr, child_addr, child_ptr, FAIL)
+
+    if(parent_ptr && child_ptr) {
+        HDassert(parent_ptr->magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
+        HDassert(child_ptr->magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
+
+        if(child_ptr->flush_dep_nparents > 0) {
+            unsigned u;         /* Local index variable */
+
+            HDassert(child_ptr->flush_dep_parent);
+            HDassert(child_ptr->flush_dep_parent_nalloc >= child_ptr->flush_dep_nparents);
+
+            for(u = 0; u < child_ptr->flush_dep_nparents; u++) {
+                if(child_ptr->flush_dep_parent[u] == parent_ptr) {
+                    fd_exists = TRUE;
+                    HDassert(parent_ptr->flush_dep_nchildren > 0);
+                    break;
+                } /* end if */
+            } /* end for */
+        } /* end if */
+    } /* end if */
+
+    *fd_exists_ptr = fd_exists;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5C_flush_dependency_exists() */
+#endif /* NDEBUG */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function:    H5C_validate_index_list
+ *
+ * Purpose:     Debugging function that scans the index list for errors.
+ *
+ *		If an error is detected, the function generates a
+ *		diagnostic and returns FAIL.  If no error is detected,
+ *		the function returns SUCCEED.
+ *
+ * Return:      FAIL if error is detected, SUCCEED otherwise.
+ *
+ * Programmer:  John Mainzer, 9/16/16
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+herr_t
+H5C_validate_index_list(H5C_t *cache_ptr)
+{
+    H5C_cache_entry_t *	entry_ptr = NULL;
+    uint32_t            len = 0;
+    int32_t		index_ring_len[H5C_RING_NTYPES];
+    size_t              size = 0;
+    size_t              clean_size = 0;
+    size_t              dirty_size = 0;
+    size_t		index_ring_size[H5C_RING_NTYPES];
+    size_t		clean_index_ring_size[H5C_RING_NTYPES];
+    size_t		dirty_index_ring_size[H5C_RING_NTYPES];
+    int			i;
+    herr_t		ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    /* Sanity checks */
+    HDassert(cache_ptr);
+    HDassert(cache_ptr->magic == H5C__H5C_T_MAGIC);
+
+    for(i = 0; i < H5C_RING_NTYPES; i++) {
+	index_ring_len[i] = 0;
+	index_ring_size[i] = 0;
+	clean_index_ring_size[i] = 0;
+	dirty_index_ring_size[i] = 0;
+    } /* end if */
+
+    if(((cache_ptr->il_head == NULL) || (cache_ptr->il_tail == NULL))
+            && (cache_ptr->il_head != cache_ptr->il_tail))
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Check 1 failed")
+
+    if((cache_ptr->index_len == 1) && ((cache_ptr->il_head != cache_ptr->il_tail)
+            || (cache_ptr->il_head == NULL) || (cache_ptr->il_head->size != cache_ptr->index_size)))
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Check 2 failed")
+
+    if((cache_ptr->index_len >= 1)
+            && ((cache_ptr->il_head == NULL)
+                || (cache_ptr->il_head->il_prev != NULL)
+                || (cache_ptr->il_tail == NULL)
+                || (cache_ptr->il_tail->il_next != NULL)))
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Check 3 failed")
+
+    entry_ptr = cache_ptr->il_head;
+    while(entry_ptr != NULL) {
+        if((entry_ptr != cache_ptr->il_head)
+                && ((entry_ptr->il_prev == NULL) || (entry_ptr->il_prev->il_next != entry_ptr)))
+            HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Check 4 failed")
+
+        if((entry_ptr != cache_ptr->il_tail)
+                && ((entry_ptr->il_next == NULL) || (entry_ptr->il_next->il_prev != entry_ptr)))
+            HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Check 5 failed")
+
+	HDassert(entry_ptr->ring > 0);
+	HDassert(entry_ptr->ring < H5C_RING_NTYPES);
+
+        len++;
+	index_ring_len[entry_ptr->ring] += 1;
+
+        size += entry_ptr->size;
+        index_ring_size[entry_ptr->ring] += entry_ptr->size;
+
+	if(entry_ptr->is_dirty) {
+	    dirty_size += entry_ptr->size;
+	    dirty_index_ring_size[entry_ptr->ring] += entry_ptr->size;
+	} /* end if */
+        else {
+	    clean_size += entry_ptr->size;
+	    clean_index_ring_size[entry_ptr->ring] += entry_ptr->size;
+	} /* end else */
+
+        entry_ptr = entry_ptr->il_next;
+    } /* end while */
+
+    if((cache_ptr->index_len != len) || (cache_ptr->il_len != len)
+            || (cache_ptr->index_size != size) || (cache_ptr->il_size != size)
+            || (cache_ptr->clean_index_size != clean_size)
+            || (cache_ptr->dirty_index_size != dirty_size)
+            || (clean_size + dirty_size != size))
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Check 6 failed")
+
+    size = 0;
+    clean_size = 0;
+    dirty_size = 0;
+    for(i = 0; i < H5C_RING_NTYPES; i++) {
+	size += clean_index_ring_size[i] + dirty_index_ring_size[i];
+	clean_size += clean_index_ring_size[i];
+	dirty_size += dirty_index_ring_size[i];
+    } /* end for */
+
+    if((cache_ptr->index_size != size)
+            || (cache_ptr->clean_index_size != clean_size)
+            || (cache_ptr->dirty_index_size != dirty_size))
+        HGOTO_ERROR(H5E_CACHE, H5E_SYSTEM, FAIL, "Check 7 failed")
+
+done:
+    if(ret_value != SUCCEED)
+        HDassert(0);
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5C_validate_index_list() */
+#endif /* NDEBUG */
+
+
+/*-------------------------------------------------------------------------
+ *
+ * Function:    H5C_get_entry_ptr_from_addr()
+ *
+ * Purpose:     Debugging function that attempts to look up an entry in the 
+ *              cache by its file address, and if found, returns a pointer 
+ *              to the entry in *entry_ptr_ptr.  If the entry is not in the 
+ *              cache, *entry_ptr_ptr is set to NULL.
+ *
+ *              WARNING: This call should be used only in debugging  
+ *                       routines, and it should be avoided when 
+ *                       possible.
+ *
+ *                       Further, if we ever multi-thread the cache, 
+ *                       this routine will have to be either discarded 
+ *                       or heavily re-worked.
+ *
+ *                       Finally, keep in mind that the entry whose 
+ *                       pointer is obtained in this fashion may not 
+ *                       be in a stable state.  
+ *
+ *              Note that this function is only defined if NDEBUG
+ *              is not defined.
+ *
+ *              As heavy use of this function is almost certainly a 
+ *              bad idea, the metadata cache tracks the number of 
+ *              successful calls to this function, and (if 
+ *              H5C_DO_SANITY_CHECKS is defined) displays any 
+ *              non-zero count on cache shutdown.
+ *
+ * Return:      FAIL if error is detected, SUCCEED otherwise.
+ *
+ * Programmer:  John Mainzer, 5/30/14
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+herr_t
+H5C_get_entry_ptr_from_addr(H5C_t *cache_ptr, haddr_t addr, void **entry_ptr_ptr)
+{
+    H5C_cache_entry_t * entry_ptr = NULL;
+    herr_t		ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Sanity checks */
+    HDassert(cache_ptr);
+    HDassert(cache_ptr->magic == H5C__H5C_T_MAGIC);
+    HDassert(H5F_addr_defined(addr));
+    HDassert(entry_ptr_ptr);
+
+    H5C__SEARCH_INDEX(cache_ptr, addr, entry_ptr, FAIL)
+
+    if(entry_ptr == NULL)
+        /* the entry doesn't exist in the cache -- report this
+         * and quit.
+         */
+        *entry_ptr_ptr = NULL;
+    else {
+        *entry_ptr_ptr = entry_ptr;
+
+	/* increment call counter */
+	(cache_ptr->get_entry_ptr_from_addr_counter)++;
+    } /* end else */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5C_get_entry_ptr_from_addr() */
+#endif /* NDEBUG */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5C_get_serialization_in_progress
+ *
+ * Purpose:     Return the current value of 
+ *              cache_ptr->serialization_in_progress.
+ *
+ * Return:      Current value of cache_ptr->serialization_in_progress.
+ *
+ * Programmer:  John Mainzer
+ *		8/24/15
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+hbool_t
+H5C_get_serialization_in_progress(const H5C_t *cache_ptr)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    /* Sanity check */
+    HDassert(cache_ptr);
+    HDassert(cache_ptr->magic == H5C__H5C_T_MAGIC);
+
+    FUNC_LEAVE_NOAPI(cache_ptr->serialization_in_progress)
+} /* H5C_get_serialization_in_progress() */
+#endif /* NDEBUG */
+
+
 /*-------------------------------------------------------------------------
  *
  * Function:    H5C_cache_is_clean()
@@ -995,3 +1334,69 @@ H5C_cache_is_clean(const H5C_t *cache_ptr, H5C_ring_t inner_ring)
 } /* H5C_cache_is_clean() */
 #endif /* NDEBUG */
 
+
+/*-------------------------------------------------------------------------
+ *
+ * Function:    H5C_verify_entry_type()
+ *
+ * Purpose:     Debugging function that attempts to look up an entry in the 
+ *		cache by its file address, and if found, test to see if its
+ *		type field contains the expted value.
+ *
+ *		If the specified entry is in cache, *in_cache_ptr is set
+ *		to TRUE, and *type_ok_ptr is set to TRUE or FALSE depending 
+ *		on whether the entries type field matches the expected_type 
+ *		parameter.
+ *
+ *		If the target entry is not in cache, *in_cache_ptr is 
+ *		set to FALSE, and *type_ok_ptr is undefined.
+ *
+ *		Note that this function is only defined if NDEBUG
+ *		is not defined.
+ *
+ * Return:      FAIL if error is detected, SUCCEED otherwise.
+ *
+ * Programmer:  John Mainzer, 5/30/14
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NDEBUG
+herr_t
+H5C_verify_entry_type(H5C_t *cache_ptr, haddr_t addr,
+    const H5C_class_t *expected_type, hbool_t *in_cache_ptr,
+    hbool_t *type_ok_ptr)
+{
+    H5C_cache_entry_t * entry_ptr = NULL;
+    herr_t              ret_value = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Sanity checks */
+    HDassert(cache_ptr);
+    HDassert(cache_ptr->magic == H5C__H5C_T_MAGIC);
+    HDassert(H5F_addr_defined(addr));
+    HDassert(expected_type);
+    HDassert(in_cache_ptr);
+    HDassert(type_ok_ptr);
+
+    H5C__SEARCH_INDEX(cache_ptr, addr, entry_ptr, FAIL)
+
+    if(entry_ptr == NULL)
+        /* the entry doesn't exist in the cache -- report this
+         * and quit.
+         */
+        *in_cache_ptr = FALSE;
+    else {
+        *in_cache_ptr = TRUE;
+
+	if(entry_ptr->prefetched)
+	    *type_ok_ptr = (expected_type->id == entry_ptr->prefetch_type_id);
+	else
+	    *type_ok_ptr = (expected_type == entry_ptr->type);
+    } /* end else */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5C_verify_entry_type() */
+#endif /* NDEBUG */
+
diff --git a/src/H5Cpkg.h b/src/H5Cpkg.h
index f237b7b..1656a32 100644
--- a/src/H5Cpkg.h
+++ b/src/H5Cpkg.h
@@ -682,6 +682,31 @@ if ( ( ( ( (head_ptr) == NULL ) || ( (tail_ptr) == NULL ) ) &&             \
 #define H5C__UPDATE_STATS_FOR_INDEX_SCAN_RESTART(cache_ptr) \
 	((cache_ptr)->index_scan_restarts)++;
 
+#define H5C__UPDATE_STATS_FOR_CACHE_IMAGE_CREATE(cache_ptr) \
+{                                                           \
+    (cache_ptr)->images_created++;                          \
+}
+
+#define H5C__UPDATE_STATS_FOR_CACHE_IMAGE_LOAD(cache_ptr)  \
+{                                                          \
+    /* make sure image len is still good */                \
+    HDassert((cache_ptr)->image_len > 0);                  \
+    (cache_ptr)->images_loaded++;                          \
+    (cache_ptr)->last_image_size = (cache_ptr)->image_len; \
+}
+
+#define H5C__UPDATE_STATS_FOR_PREFETCH(cache_ptr, dirty) \
+{                                                        \
+    (cache_ptr)->prefetches++;                           \
+    if ( dirty )                                         \
+        (cache_ptr)->dirty_prefetches++;                 \
+}
+
+#define H5C__UPDATE_STATS_FOR_PREFETCH_HIT(cache_ptr) \
+{                                                     \
+    (cache_ptr)->prefetch_hits++;                     \
+}
+
 #if H5C_COLLECT_CACHE_ENTRY_STATS
 
 #define H5C__RESET_CACHE_ENTRY_STATS(entry_ptr) \
@@ -906,6 +931,10 @@ if ( ( ( ( (head_ptr) == NULL ) || ( (tail_ptr) == NULL ) ) &&             \
 #define H5C__UPDATE_STATS_FOR_SLIST_SCAN_RESTART(cache_ptr)
 #define H5C__UPDATE_STATS_FOR_LRU_SCAN_RESTART(cache_ptr)
 #define H5C__UPDATE_STATS_FOR_INDEX_SCAN_RESTART(cache_ptr)
+#define H5C__UPDATE_STATS_FOR_CACHE_IMAGE_CREATE(cache_ptr)
+#define H5C__UPDATE_STATS_FOR_CACHE_IMAGE_LOAD(cache_ptr)
+#define H5C__UPDATE_STATS_FOR_PREFETCH(cache_ptr, dirty)
+#define H5C__UPDATE_STATS_FOR_PREFETCH_HIT(cache_ptr)
 
 #endif /* H5C_COLLECT_CACHE_STATS */
 
@@ -2219,6 +2248,120 @@ if ( ( (cache_ptr)->index_size !=                                           \
 
 /*-------------------------------------------------------------------------
  *
+ * Macro:	H5C__UPDATE_RP_FOR_INSERT_APPEND
+ *
+ * Purpose:     Update the replacement policy data structures for an
+ *		insertion of the specified cache entry.  
+ *
+ *		Unlike H5C__UPDATE_RP_FOR_INSERTION below, mark the 
+ *		new entry as the LEAST recently used entry, not the 
+ *		most recently used.  
+ *
+ *		For now at least, this macro should only be used in 
+ *		the reconstruction of the metadata cache from a cache 
+ *		image block.
+ *
+ *		At present, we only support the modified LRU policy, so
+ *		this function deals with that case unconditionally.  If
+ *		we ever support other replacement policies, the function
+ *		should switch on the current policy and act accordingly.
+ *
+ * Return:      N/A
+ *
+ * Programmer:  John Mainzer, 8/15/15
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#if H5C_MAINTAIN_CLEAN_AND_DIRTY_LRU_LISTS
+
+#define H5C__UPDATE_RP_FOR_INSERT_APPEND(cache_ptr, entry_ptr, fail_val)   \
+{                                                                          \
+    HDassert( (cache_ptr) );                                               \
+    HDassert( (cache_ptr)->magic == H5C__H5C_T_MAGIC );                    \
+    HDassert( (entry_ptr) );                                               \
+    HDassert( !((entry_ptr)->is_protected) );                              \
+    HDassert( !((entry_ptr)->is_read_only) );                              \
+    HDassert( ((entry_ptr)->ro_ref_count) == 0 );                          \
+    HDassert( (entry_ptr)->size > 0 );                                     \
+                                                                           \
+    if ( (entry_ptr)->is_pinned ) {                                        \
+                                                                           \
+        H5C__DLL_PREPEND((entry_ptr), (cache_ptr)->pel_head_ptr,           \
+                         (cache_ptr)->pel_tail_ptr,                        \
+                         (cache_ptr)->pel_len,                             \
+                         (cache_ptr)->pel_size, (fail_val))                \
+                                                                           \
+    } else {                                                               \
+                                                                           \
+        /* modified LRU specific code */                                   \
+                                                                           \
+        /* insert the entry at the tail of the LRU list. */                \
+                                                                           \
+        H5C__DLL_APPEND((entry_ptr), (cache_ptr)->LRU_head_ptr,            \
+                        (cache_ptr)->LRU_tail_ptr,                         \
+		        (cache_ptr)->LRU_list_len,                         \
+                        (cache_ptr)->LRU_list_size, (fail_val))            \
+                                                                           \
+        /* insert the entry at the tail of the clean or dirty LRU list as  \
+         * appropriate.                                                    \
+         */                                                                \
+                                                                           \
+        if ( entry_ptr->is_dirty ) {                                       \
+            H5C__AUX_DLL_APPEND((entry_ptr), (cache_ptr)->dLRU_head_ptr,   \
+                                (cache_ptr)->dLRU_tail_ptr,                \
+                                (cache_ptr)->dLRU_list_len,                \
+                                (cache_ptr)->dLRU_list_size, (fail_val))   \
+        } else {                                                           \
+            H5C__AUX_DLL_APPEND((entry_ptr), (cache_ptr)->cLRU_head_ptr,   \
+                                (cache_ptr)->cLRU_tail_ptr,                \
+                                (cache_ptr)->cLRU_list_len,                \
+                                (cache_ptr)->cLRU_list_size, (fail_val))   \
+        }                                                                  \
+                                                                           \
+        /* End modified LRU specific code. */                              \
+    }                                                                      \
+}
+
+#else /* H5C_MAINTAIN_CLEAN_AND_DIRTY_LRU_LISTS */
+
+#define H5C__UPDATE_RP_FOR_INSERT_APPEND(cache_ptr, entry_ptr, fail_val)   \
+{                                                                          \
+    HDassert( (cache_ptr) );                                               \
+    HDassert( (cache_ptr)->magic == H5C__H5C_T_MAGIC );                    \
+    HDassert( (entry_ptr) );                                               \
+    HDassert( !((entry_ptr)->is_protected) );                              \
+    HDassert( !((entry_ptr)->is_read_only) );                              \
+    HDassert( ((entry_ptr)->ro_ref_count) == 0 );                          \
+    HDassert( (entry_ptr)->size > 0 );                                     \
+                                                                           \
+    if ( (entry_ptr)->is_pinned ) {                                        \
+                                                                           \
+        H5C__DLL_PREPEND((entry_ptr), (cache_ptr)->pel_head_ptr,           \
+                         (cache_ptr)->pel_tail_ptr,                        \
+                         (cache_ptr)->pel_len,                             \
+                         (cache_ptr)->pel_size, (fail_val))                \
+	                                                                   \
+    } else {                                                               \
+                                                                           \
+        /* modified LRU specific code */                                   \
+                                                                           \
+        /* insert the entry at the tail of the LRU list. */                \
+                                                                           \
+        H5C__DLL_APPEND((entry_ptr), (cache_ptr)->LRU_head_ptr,            \
+                        (cache_ptr)->LRU_tail_ptr,                         \
+			(cache_ptr)->LRU_list_len,                         \
+                        (cache_ptr)->LRU_list_size, (fail_val))            \
+                                                                           \
+        /* End modified LRU specific code. */                              \
+    }                                                                      \
+}
+
+#endif /* H5C_MAINTAIN_CLEAN_AND_DIRTY_LRU_LISTS */
+
+
+/*-------------------------------------------------------------------------
+ *
  * Macro:	H5C__UPDATE_RP_FOR_INSERTION
  *
  * Purpose:     Update the replacement policy data structures for an
@@ -3962,7 +4105,22 @@ typedef struct H5C_tag_info_t {
  *
  * size_decreased:  Boolean flag set to TRUE whenever the maximum cache
  *		size is decreased.  The flag triggers a call to
- *		H5C_make_space_in_cache() on the next call to H5C_protect().
+ *		H5C__make_space_in_cache() on the next call to H5C_protect().
+ *
+ * resize_in_progress: As the metadata cache has become re-entrant, it is 
+ *		possible that a protect may trigger a call to 
+ *		H5C__auto_adjust_cache_size(), which may trigger a flush,
+ *		which may trigger a protect, which will result in another 
+ *		call to H5C__auto_adjust_cache_size().  
+ *
+ *		The resize_in_progress boolean flag is used to detect this,
+ *		and to prevent the infinite recursion that would otherwise
+ *		occur.
+ *
+ *		Note that this issue is not hypothetical -- this field 
+ *		was added 12/29/15 to fix a bug exposed in the testing 
+ *		of changes to the file driver info superblock extension
+ *		management code needed to support rings.
  *
  * resize_ctl:	Instance of H5C_auto_size_ctl_t containing configuration
  * 		data for automatic cache resizing.
@@ -4039,6 +4197,77 @@ typedef struct H5C_tag_info_t {
  *	this field will be reset every automatic resize epoch.
  *
  *
+ * Metadata cache image management related fields.
+ *
+ * image_ctl:	Instance of H5C_cache_image_ctl_t containing configuration
+ * 		data for generation of a cache image on file close.
+ *
+ * serialization_in_progress:  Boolean field that is set to TRUE iff
+ *		the cache is in the process of being serialized.  This 
+ *		field is needed to support the H5C_serialization_in_progress()
+ *		call, which is in turn required for sanity checks in some
+ *		cache clients.
+ *
+ * load_image:	Boolean flag indicating that the metadata cache image 
+ *		superblock extension message exists and should be 
+ *		read, and the image block read and decoded on the next
+ *		call to H5C_protect().  
+ *
+ * image_loaded:  Boolean flag indicating that the metadata cache has 
+ *              loaded the metadata cache image as directed by the 
+ *              MDC cache image superblock extension message.
+ *
+ * delete_image: Boolean flag indicating whether the metadata cache image
+ *		superblock message should be deleted and the cache image
+ *		file space freed after they have been read and decoded.
+ *
+ *		This flag should be set to TRUE iff the file is opened 
+ *		R/W and there is a cache image to be read.
+ *
+ * image_addr:  haddr_t containing the base address of the on disk 
+ *		metadata cache image, or HADDR_UNDEF if that value is 
+ *		undefined.  Note that this field is used both in the 
+ *		construction and write, and the read and decode of 
+ *		metadata cache image blocks.
+ *
+ * image_len:	hsize_t containing the size of the on disk metadata cache 
+ *		image, or zero if that value is undefined.  Note that this 
+ *		field is used both in the construction and write, and the 
+ *		read and decode of metadata cache image blocks.
+ *
+ * image_data_len:  size_t containing the number of bytes of data in the 
+ *		on disk metadata cache image, or zero if that value is 
+ *		undefined.
+ *
+ *		In most cases, this value is the same as the image_len
+ *		above.  It exists to allow for metadata cache image blocks
+ *		that are larger than the actual image.  Thus in all 
+ *		cases image_data_len <= image_len.
+ *
+ * To create the metadata cache image, we must first serialize all the
+ * entries in the metadata cache.  This is done by a scan of the index.
+ * As entries must be serialized in increasing flush dependency height
+ * order, we scan the index repeatedly, once for each flush dependency
+ * height in increasing order.
+ *
+ * This operation is complicated by the fact that entries other the the
+ * target may be inserted, loaded, relocated, or removed from the cache 
+ * (either by eviction or the take ownership flag) as the result of a 
+ * pre_serialize or serialize callback.  While entry removals are not 
+ * a problem for the scan of the index, insertions, loads, and relocations
+ * are.  Hence the entries loaded, inserted, and relocated counters 
+ * listed below have been implemented to allow these conditions to be 
+ * detected and dealt with by restarting the scan.
+ *
+ * The serialization operation is further complicated by the fact that 
+ * the flush dependency height of a given entry may increase (as the 
+ * result of an entry load or insert) or decrease (as the result of an 
+ * entry removal -- via either eviction or the take ownership flag).  The
+ * entry_fd_height_change_counter field is maintained to allow detection
+ * of this condition, and a restart of the scan when it occurs.
+ *
+ * Note that all these new fields would work just as well as booleans.
+ *
  * entries_loaded_counter: Number of entries loaded into the cache 
  *		since the last time this field was reset.
  *
@@ -4048,6 +4277,29 @@ typedef struct H5C_tag_info_t {
  * entries relocated_counter: Number of entries whose base address has
  *		been changed since the last time this field was reset.
  *
+ * entry_fd_height_change_counter: Number of entries whose flush dependency
+ *		height has changed since the last time this field was reset.
+ *
+ * The following fields are used assemble the cache image prior to 
+ * writing it to disk.
+ *
+ * num_entries_in_image: Unsigned integer field containing the number of entries
+ *		to be copied into the metadata cache image.  Note that 
+ *		this value will be less than the number of entries in 
+ *		the cache, and the superblock and its related entries 
+ *		are not written to the metadata cache image.
+ *
+ * image_entries: Pointer to a dynamically allocated array of instance of
+ *		H5C_image_entry_t of length num_entries_in_image, or NULL
+ *		if that array does not exist.  This array is used to
+ *		assemble entry data to be included in the image, and to 
+ *		sort them by flush dependency height and LRU rank.
+ * 
+ * image_buffer: Pointer to the dynamically allocated buffer of length
+ *		image_len in which the metadata cache image is assembled, 
+ *		or NULL if that	buffer does not exist.
+ *
+ *
  * Free Space Manager Related fields:
  *
  * The free space managers must be informed when we are about to close 
@@ -4261,23 +4513,63 @@ typedef struct H5C_tag_info_t {
  * max_pel_size: Largest value attained by the pel_size field in the
  *              current epoch.
  *
- * calls_to_msic: Total number of calls to H5C_make_space_in_cache
+ * calls_to_msic: Total number of calls to H5C__make_space_in_cache
  *
  * total_entries_skipped_in_msic: Number of clean entries skipped while
- *              enforcing the min_clean_fraction in H5C_make_space_in_cache().
+ *              enforcing the min_clean_fraction in H5C__make_space_in_cache().
  *
  * total_entries_scanned_in_msic: Number of clean entries skipped while
- *              enforcing the min_clean_fraction in H5C_make_space_in_cache().
+ *              enforcing the min_clean_fraction in H5C__make_space_in_cache().
  *
  * max_entries_skipped_in_msic: Maximum number of clean entries skipped
- *              in any one call to H5C_make_space_in_cache().
+ *              in any one call to H5C__make_space_in_cache().
  *
  * max_entries_scanned_in_msic: Maximum number of entries scanned over
- *              in any one call to H5C_make_space_in_cache().
+ *              in any one call to H5C__make_space_in_cache().
  *
  * entries_scanned_to_make_space: Number of entries scanned only when looking
  *              for entries to evict in order to make space in cache.
  *
+ *
+ * The following fields track statistics on cache images.  
+ *
+ * images_created:  Integer field containing the number of cache images
+ *		created since the last time statistics were reset.  
+ *
+ *		At present, this field must always be either 0 or 1.
+ *		Further, since cache images are only created at file 
+ *		close, this field should only be set at that time.
+ *
+ * images_loaded:  Integer field containing the number of cache images
+ *		loaded since the last time statistics were reset.
+ *
+ *		At present, this field must always be either 0 or 1.
+ *		Further, since cache images are only loaded at the 
+ *		time of the first protect or on file close, this value
+ *		should only change on those events.
+ *
+ * last_image_size:  Size of the most recently loaded metadata cache image
+ *             loaded into the cache, or zero if no image has been
+ *             loaded.  
+ *
+ *             At present, at most one cache image can be loaded into 
+ *             the metadata cache for any given file, and this image
+ *             will be loaded either on the first protect, or on file
+ *             close if no entry is protected before then.
+ *
+ *
+ * Fields for tracking prefetched entries.  Note that flushes and evictions
+ * of prefetched entries are tracked in the flushes and evictions arrays 
+ * discused above.
+ *
+ * prefetches:	Number of prefetched entries that are loaded to the 
+ *		cache.
+ *
+ * dirty_prefetches:  Number of dirty prefetched entries that are loaded
+ *		into the cache.
+ *
+ * prefetch_hits:  Number of prefetched entries that are actually used.
+ *
  * 
  * As entries are now capable of moving, loading, dirtying, and deleting 
  * other entries in their pre_serialize and serialize callbacks, it has 
@@ -4348,6 +4640,11 @@ typedef struct H5C_tag_info_t {
  *		field is intended to allow marking of output of with
  *		the processes mpi rank.
  *
+ * get_entry_ptr_from_addr_counter: Counter used to track the number of
+ *              times the H5C_get_entry_ptr_from_addr() function has been
+ *              called successfully.  This field is only defined when
+ *              NDEBUG is not #defined.
+ *
  ****************************************************************************/
 struct H5C_t {
     uint32_t			magic;
@@ -4453,6 +4750,7 @@ struct H5C_t {
     hbool_t			resize_enabled;
     hbool_t			cache_full;
     hbool_t			size_decreased;
+    hbool_t			resize_in_progress;
     H5C_auto_size_ctl_t		resize_ctl;
 
     /* Fields for epoch markers used in automatic cache size adjustment */
@@ -4468,9 +4766,23 @@ struct H5C_t {
     int64_t			cache_hits;
     int64_t			cache_accesses;
 
+    /* fields supporting generation of a cache image on file close */
+    H5C_cache_image_ctl_t	image_ctl;
+    hbool_t			serialization_in_progress;
+    hbool_t			load_image;
+    hbool_t                     image_loaded;
+    hbool_t			delete_image;
+    haddr_t 			image_addr;
+    hsize_t			image_len;
+    hsize_t			image_data_len;
     int64_t			entries_loaded_counter;
     int64_t			entries_inserted_counter;
     int64_t			entries_relocated_counter;
+    int64_t			entry_fd_height_change_counter;
+    uint32_t			num_entries_in_image;
+    H5C_image_entry_t *		image_entries;
+    void *                      image_buffer;
+
     /* Free Space Manager Related fields */
     hbool_t 			rdfsm_settled;
     hbool_t			mdfsm_settled;
@@ -4538,6 +4850,16 @@ struct H5C_t {
     int64_t			LRU_scan_restarts;
     int64_t			index_scan_restarts;
 
+    /* Fields for tracking cache image operations */
+    int32_t			images_created;
+    int32_t			images_loaded;
+    hsize_t			last_image_size;
+
+    /* Fields for tracking prefetched entries */
+    int64_t			prefetches;
+    int64_t			dirty_prefetches;
+    int64_t			prefetch_hits;
+
 #if H5C_COLLECT_CACHE_ENTRY_STATS
     int32_t                     max_accesses[H5C__MAX_NUM_TYPE_IDS + 1];
     int32_t                     min_accesses[H5C__MAX_NUM_TYPE_IDS + 1];
@@ -4549,6 +4871,10 @@ struct H5C_t {
 #endif /* H5C_COLLECT_CACHE_STATS */
 
     char			prefix[H5C__PREFIX_LEN];
+
+#ifndef NDEBUG
+    int64_t                     get_entry_ptr_from_addr_counter;
+#endif /* NDEBUG */
 };
 
 /* Define typedef for tagged cache entry iteration callbacks */
@@ -4563,12 +4889,20 @@ typedef int (*H5C_tag_iter_cb_t)(H5C_cache_entry_t *entry, void *ctx);
 /******************************/
 /* Package Private Prototypes */
 /******************************/
+H5_DLL herr_t H5C__prep_image_for_file_close(H5F_t *f, hid_t dxpl_id);
+H5_DLL herr_t H5C__deserialize_prefetched_entry(H5F_t * f, hid_t dxpl_id,
+    H5C_t * cache_ptr, H5C_cache_entry_t** entry_ptr_ptr, 
+    const H5C_class_t * type, haddr_t addr, void * udata);
 
 /* General routines */
 H5_DLL herr_t H5C__flush_single_entry(H5F_t *f, hid_t dxpl_id,
     H5C_cache_entry_t *entry_ptr, unsigned flags);
+H5_DLL herr_t H5C__generate_cache_image(H5F_t *f, hid_t dxpl_id, H5C_t *cache_ptr);
+H5_DLL herr_t H5C__load_cache_image(H5F_t *f, hid_t dxpl_id);
 H5_DLL herr_t H5C__mark_flush_dep_serialized(H5C_cache_entry_t * entry_ptr);
 H5_DLL herr_t H5C__mark_flush_dep_unserialized(H5C_cache_entry_t * entry_ptr);
+H5_DLL herr_t H5C__make_space_in_cache(H5F_t * f, hid_t   dxpl_id,
+    size_t  space_needed, hbool_t write_permitted);
 H5_DLL herr_t H5C__flush_marked_entries(H5F_t * f, hid_t dxpl_id);
 H5_DLL herr_t H5C__iter_tagged_entries(H5C_t *cache, haddr_t tag, hbool_t match_global,
     H5C_tag_iter_cb_t cb, void *cb_ctx);
diff --git a/src/H5Cprivate.h b/src/H5Cprivate.h
index d7111a8..47573f9 100644
--- a/src/H5Cprivate.h
+++ b/src/H5Cprivate.h
@@ -41,7 +41,7 @@
 /**************************/
 
 /* Cache configuration settings */
-#define H5C__MAX_NUM_TYPE_IDS   29
+#define H5C__MAX_NUM_TYPE_IDS   30
 #define H5C__PREFIX_LEN         32
 
 /* This sanity checking constant was picked out of the air.  Increase
@@ -114,6 +114,7 @@
 /* Cache configuration versions */
 #define H5C__CURR_AUTO_SIZE_CTL_VER		1
 #define H5C__CURR_AUTO_RESIZE_RPT_FCN_VER	1
+#define H5C__CURR_CACHE_IMAGE_CTL_VER		1
 
 /* Default configuration settings */
 #define H5C__DEF_AR_UPPER_THRESHHOLD		0.9999f
@@ -994,16 +995,16 @@ typedef int H5C_ring_t;
  *              just before the entry is freed.
  *
  *              This is necessary, as the LRU list can be changed out
- *              from under H5C_make_space_in_cache() by the serialize
+ *              from under H5C__make_space_in_cache() by the serialize
  *              callback which may change the size of an existing entry,
  *              and/or load a new entry while serializing the target entry.
  *
  *              This in turn can cause a recursive call to
- *              H5C_make_space_in_cache() which may either flush or evict
+ *              H5C__make_space_in_cache() which may either flush or evict
  *              the next entry that the first invocation of that function
  *              was about to examine.
  *
- *              The magic field allows H5C_make_space_in_cache() to
+ *              The magic field allows H5C__make_space_in_cache() to
  *              detect this case, and re-start its scan from the bottom
  *              of the LRU when this situation occurs.
  *
@@ -1338,6 +1339,187 @@ typedef int H5C_ring_t;
  *		In either case, when there is no previous item, it should 
  *		be NULL.
  *
+ * Fields supporting the cache image feature:
+ *
+ * The following fields are used to store data about the entry which must 
+ * be stored in the cache image block, but which will typically be either 
+ * lost or heavily altered in the process of serializing the cache and 
+ * preparing its contents to be copied into the cache image block.
+ *
+ * Some fields are also used in loading the contents of the metadata cache
+ * image back into the cache, and in managing such entries until they are 
+ * either protected by the library (at which point they become regular 
+ * entries) or are evicted.  See discussion of the prefetched field for 
+ * further details.
+ *
+ * include_in_image: Boolean flag indicating whether this entry should
+ *		be included in the metadata cache image.  This field should
+ *		always be false prior to the H5C_prep_for_file_close() call.
+ *		During that call, it should be set to TRUE for all entries
+ *		that are to be included in the metadata cache image.  At 
+ *		present, only the superblock, the superblock extension 
+ *		object header and its chunks (if any) are omitted from 
+ *		the image.
+ *
+ * lru_rank:	Rank of the entry in the LRU just prior to file close.
+ *
+ *		Note that the first entry on the LRU has lru_rank 1,
+ *		and that entries not on the LRU at that time will have 
+ *		either lru_rank -1 (if pinned) or 0 (if loaded during 
+ *		the process of flushing the cache.
+ *
+ * image_dirty: Boolean flag indicating whether the entry should be marked
+ *		as dirty in the metadata cache image.  The flag is set to
+ *		TRUE iff the entry is dirty when H5C_prep_for_file_close()
+ *		is called.
+ *
+ * fd_parent_count: If the entry is a child in one or more flush dependency 
+ *		relationships, this field contains the number of flush 
+ *		dependency parents.
+ *
+ *		In all other cases, the field is set to zero.
+ *
+ *		Note that while this count is initially taken from the 
+ *		flush dependency fields above, if the entry is in the 
+ *		cache image (i.e. include_in_image is TRUE), any parents
+ *		that are not in the image are removed from this count and
+ *		from the fd_parent_addrs array below.
+ *
+ *		Finally observe that if the entry is dirty and in the 
+ *		cache image, and its parent is dirty and not in the cache
+ *		image, then the entry must be removed from the cache image
+ *		to avoid violating the flush dependency flush ordering.
+ *
+ * fd_parent_addrs: If the entry is a child in one or more flush dependency 
+ *		relationship when H5C_prep_for_file_close() is called, this 
+ *		field must contain a pointer to an array of size 
+ *		fd_parent_count containing the on disk addresses of the 
+ *		parent.
+ *
+ *		In all other cases, the field is set to NULL.
+ *
+ *		Note that while this list of addresses is initially taken 
+ *		from the flush dependency fields above, if the entry is in the 
+ *		cache image (i.e. include_in_image is TRUE), any parents
+ *		that are not in the image are removed from this list, and 
+ *		and from the fd_parent_count above.
+ *
+ *		Finally observe that if the entry is dirty and in the 
+ *		cache image, and its parent is dirty and not in the cache
+ *		image, then the entry must be removed from the cache image
+ *		to avoid violating the flush dependency flush ordering.
+ *
+ * fd_child_count: If the entry is a parent in a flush dependency 
+ *		relationship, this field contains the number of flush 
+ *		dependency children.
+ *
+ *		In all other cases, the field is set to zero.
+ *
+ *		Note that while this count is initially taken from the 
+ *		flush dependency fields above, if the entry is in the 
+ *		cache image (i.e. include_in_image is TRUE), any children
+ *		that are not in the image are removed from this count.
+ *
+ * fd_dirty_child_count: If the entry is a parent in a flush dependency 
+ *		relationship, this field contains the number of dirty flush 
+ *		dependency children.
+ *
+ *		In all other cases, the field is set to zero.
+ *
+ *		Note that while this count is initially taken from the 
+ *		flush dependency fields above, if the entry is in the 
+ *		cache image (i.e. include_in_image is TRUE), any dirty 
+ *		children that are not in the image are removed from this 
+ *		count.
+ *
+ * image_fd_height: Flush dependency height of the entry in the cache image.
+ *
+ *		The flush dependency height of any entry involved in a 
+ *		flush dependency relationship is defined to be the 
+ *		longest flush dependency path from that entry to an entry
+ *		with no flush depenency children.  
+ *
+ *		Since the image_fd_height is used to order entries in the 
+ *		cache image so that fd parents preceed fd children, for 
+ *		purposes of this field, and entry is at flush dependency
+ *		level 0 if it either has no children, or if all of its
+ *		children are not in the cache image.  
+ *
+ *		Note that if a child in a flush dependency relationship is 
+ *		dirty and in the cache image, and its parent is dirty and
+ *		not in the cache image, then the child must be excluded 
+ *		from the cache image to maintain flush ordering.
+ *
+ * prefetched:	Boolean flag indicating that the on disk image of the entry
+ *		has been loaded into the cache prior any request for the 
+ *		entry by the rest of the library.
+ *
+ *		As of this writing (8/10/15), this can only happen through 
+ *		the load of a cache image block, although other scenarios 
+ *		are contemplated for the use of this feature.  Note that 
+ *		unlike the usual prefetch situation, this means that a 
+ *		pre fetched entry can be dirty, and/or can be a party to 
+ *		flush dependency relationship(s).  This complicates matters 
+ *		somewhat.
+ *
+ *		The essential feature of a pre-fetched entry is that it 
+ *		consists only of a buffer containing the on disk image of 
+ *		the entry.  Thus it must be  deserialized before it can 
+ *		be passed back to the library on a protect call.  This 
+ *		task is handled by H5C_deserialized_prefetched_entry().
+ *		In essence, this routine calls the deserialize callback 
+ *		provided in the protect call with the on disk image, 
+ *		deletes the prefetched entry from the cache, and replaces
+ *		it with the deserialized entry returned by the deserialize
+ *		callback.
+ *
+ *		Further, if the prefetched entry is a flush dependency parent, 
+ *		all its flush dependency children (which must also be 
+ *		pre-fetched entries), must be tranfered to the new cache 
+ *		entry returned by the deserailization callback.
+ *
+ *		Finally, if the prefetched entry is a flush dependency child, 
+ *		this flush dependency must be destroyed prior to the 
+ *		deserialize call.
+ *
+ *		In addition to the above special processing on the first 
+ *		protect call on a prefetched entry (after which is no longer
+ *		a prefetched entry), prefetched entries also require special 
+ *		tretment on flush and evict.
+ *
+ *		On flush, a dirty prefetched entry must simply be written 
+ *		to disk and marked clean without any call to any client 
+ *		callback.
+ *
+ *		On eviction, if a prefetched entry is a flush dependency 
+ *		child, that flush dependency relationship must be destroyed
+ *		just prior to the eviction.  If the flush dependency code
+ *		is working properly, it should be impossible for any entry
+ *		that is a flush dependency parent to be evicted.
+ *
+ * prefetch_type_id: Integer field containing the type ID of the prefetched
+ *		entry.  This ID must match the ID of the type provided in any
+ *		protect call on the prefetched entry.
+ *
+ *		The value of this field is undefined in prefetched is FALSE.
+ *
+ * age:		Number of times a prefetched entry has appeared in 
+ *		subsequent cache images. The field exists to allow 
+ *		imposition of a limit on how many times a prefetched 
+ *		entry can appear in subsequent cache images without being
+ *		converted to a regular entry.
+ *
+ *		This field must be zero if prefetched is FALSE.  
+ *
+ * serialization_count:  Integer field used to maintain a count of the 
+ *		number of times each entry is serialized during cache 
+ *		serialization.  While no entry should be serialized more than
+ *		once in any serialization call, throw an assertion if any 
+ *		flush depencency parent is serialized more than once during 
+ *		a single cache serialization.
+ *
+ *		This is a debugging field, and thus is maintained only if 
+ *		NDEBUG is undefined.
  *
  * Fields supporting tagged entries:
  *
@@ -1433,6 +1615,23 @@ typedef struct H5C_cache_entry_t {
     struct H5C_cache_entry_t   *coll_prev;
 #endif /* H5_HAVE_PARALLEL */
 
+    /* fields supporting cache image */
+    hbool_t                     include_in_image;
+    int32_t                     lru_rank;
+    hbool_t                     image_dirty;
+    uint64_t                    fd_parent_count;
+    haddr_t                    *fd_parent_addrs;
+    uint64_t                    fd_child_count;
+    uint64_t                    fd_dirty_child_count;
+    uint32_t                    image_fd_height;
+    hbool_t                     prefetched;
+    int                         prefetch_type_id;
+    int32_t                     age;
+
+#ifndef NDEBUG	/* debugging field */
+    int                         serialization_count;
+#endif /* NDEBUG */
+
     /* fields supporting tag lists */
     struct H5C_cache_entry_t   *tl_next;
     struct H5C_cache_entry_t   *tl_prev;
@@ -1447,6 +1646,168 @@ typedef struct H5C_cache_entry_t {
 #endif /* H5C_COLLECT_CACHE_ENTRY_STATS */
 } H5C_cache_entry_t;
 
+
+/****************************************************************************
+ *
+ * structure H5C_image_entry_t
+ *
+ * Instances of the H5C_image_entry_t structure are used to store data on
+ * metadata cache entries used in the construction of the metadata cache 
+ * image block.  In essence this structure is a greatly simplified version
+ * of H5C_cache_entry_t.
+ *
+ * The fields of this structure are discussed individually below:
+ *
+ *						JRM - 8/5/15
+ *
+ * magic:	Unsigned 32 bit integer that must always be set to
+ *              H5C__H5C_IMAGE_ENTRY_T_MAGIC when the entry is valid.
+ *              The field must be set to H5C__H5C_IMAGE__ENTRY_T_BAD_MAGIC
+ *              just before the entry is freed.
+ *
+ * addr:	Base address of the cache entry on disk.
+ *
+ * size:	Length of the cache entry on disk in bytes.
+ *
+ * ring:	Instance of H5C_ring_t indicating the flush ordering ring 
+ *		to which this entry is assigned.
+ *
+ * age:		Number of times this prefetech entry has appeared in 
+ *		the current sequence of cache images.  This field is 
+ *		initialized to 0 if the instance of H5C_image_entry_t
+ *		is constructed from a regular entry.  
+ *
+ *		If the instance is constructed from a prefetched entry 
+ *		currently residing in the metadata cache, the field is
+ *		set to 1 + the age of the prefetched entry, or to 
+ *		H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX if that sum exceeds
+ *		H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX.
+ *
+ * type_id:	Integer field containing the type ID of the entry.
+ *
+ * lru_rank:	Rank of the entry in the LRU just prior to file close.
+ *
+ *		Note that the first entry on the LRU has lru_rank 1,
+ *		and that entries not on the LRU at that time will have 
+ *		either lru_rank -1 (if pinned) or 0 (if loaded during 
+ *		the process of flushing the cache.
+ *
+ * is_dirty:	Boolean flag indicating whether the contents of the cache
+ *		entry has been modified since the last time it was written
+ *		to disk as a regular piece of metadata.
+ *
+ * image_fd_height: Flush dependency height of the entry in the cache image.
+ *
+ *              The flush dependency height of any entry involved in a
+ *              flush dependency relationship is defined to be the
+ *              longest flush dependency path from that entry to an entry
+ *              with no flush depenency children.
+ *
+ *              Since the image_fd_height is used to order entries in the
+ *              cache image so that fd parents preceed fd children, for
+ *              purposes of this field, an entry is at flush dependency
+ *              level 0 if it either has no children, or if all of its
+ *              children are not in the cache image.
+ *
+ *              Note that if a child in a flush dependency relationship is
+ *              dirty and in the cache image, and its parent is dirty and
+ *              not in the cache image, then the child must be excluded
+ *              from the cache image to maintain flush ordering.
+ *
+ * fd_parent_count: If the entry is a child in one or more flush dependency
+ *              relationships, this field contains the number of flush
+ *              dependency parents.
+ *
+ *              In all other cases, the field is set to zero.
+ *
+ *              Note that while this count is initially taken from the
+ *              flush dependency fields in the associated instance of 
+ *		H5C_cache_entry_t, if the entry is in the cache image 
+ *		(i.e. include_in_image is TRUE), any parents that are 
+ *		not in the image are removed from this count and
+ *              from the fd_parent_addrs array below.
+ *
+ *              Finally observe that if the entry is dirty and in the
+ *              cache image, and its parent is dirty and not in the cache
+ *              image, then the entry must be removed from the cache image
+ *              to avoid violating the flush dependency flush ordering.
+ *		This should have happened before the construction of 
+ *		the instance of H5C_image_entry_t.
+ *
+ * fd_parent_addrs: If the entry is a child in one or more flush dependency
+ *              relationship when H5C_prep_for_file_close() is called, this
+ *              field must contain a pointer to an array of size
+ *              fd_parent_count containing the on disk addresses of the
+ *              parents.
+ *
+ *              In all other cases, the field is set to NULL.
+ *
+ *              Note that while this list of addresses is initially taken
+ *              from the flush dependency fields in the associated instance of
+ *              H5C_cache_entry_t, if the entry is in the cache image 
+ *		(i.e. include_in_image is TRUE), any parents that are not 
+ *		in the image are removed from this list, and from the 
+ *		fd_parent_count above.
+ *
+ *              Finally observe that if the entry is dirty and in the
+ *              cache image, and its parent is dirty and not in the cache
+ *              image, then the entry must be removed from the cache image
+ *              to avoid violating the flush dependency flush ordering.
+ *		This should have happened before the construction of 
+ *		the instance of H5C_image_entry_t.
+ *
+ * fd_child_count: If the entry is a parent in a flush dependency 
+ *		relationship, this field contains the number of flush 
+ *		dependency children.
+ *
+ *		In all other cases, the field is set to zero.
+ *
+ *              Note that while this count is initially taken from the
+ *              flush dependency fields in the associated instance of
+ *              H5C_cache_entry_t, if the entry is in the cache image 
+ *		(i.e. include_in_image is TRUE), any children
+ *              that are not in the image are removed from this count.
+ *
+ * fd_dirty_child_count: If the entry is a parent in a flush dependency
+ *              relationship, this field contains the number of dirty flush
+ *              dependency children.
+ *
+ *              In all other cases, the field is set to zero.
+ *
+ *              Note that while this count is initially taken from the
+ *              flush dependency fields in the associated instance of
+ *              H5C_cache_entry_t, if the entry is in the cache image 
+ *		(i.e. include_in_image is TRUE), any dirty children 
+ *		that are not in the image are removed from this count.
+ *
+ * image_ptr:	Pointer to void.  When not NULL, this field points to a
+ * 		dynamically allocated block of size bytes in which the
+ * 		on disk image of the metadata cache entry is stored.
+ *
+ * 		If the entry is dirty, the pre-serialize and serialize 
+ *		callbacks must be used to update this image before it is 
+ *		written to disk
+ *
+ *
+ ****************************************************************************/
+
+typedef struct H5C_image_entry_t {
+    uint32_t                    magic;
+    haddr_t                     addr;
+    size_t                      size;
+    H5C_ring_t                  ring;
+    int32_t                     age;
+    int32_t                     type_id;
+    int32_t                     lru_rank;
+    hbool_t                     is_dirty;
+    unsigned                    image_fd_height;
+    uint64_t                    fd_parent_count;
+    haddr_t                    *fd_parent_addrs;
+    uint64_t                    fd_child_count;
+    uint64_t                    fd_dirty_child_count;
+    void                       *image_ptr;
+} H5C_image_entry_t;
+
 /****************************************************************************
  *
  * structure H5C_auto_size_ctl_t
@@ -1736,6 +2097,92 @@ typedef struct H5C_auto_size_ctl_t {
     double				empty_reserve;
 } H5C_auto_size_ctl_t;
 
+/****************************************************************************
+ *
+ * structure H5C_cache_image_ctl_t
+ *
+ * Instances of H5C_image_ctl_t are used to get and set the control
+ * fields for generation of a metadata cache image on file close.
+ *
+ * At present control of construction of a cache image is via a FAPL
+ * property at file open / create.  
+ *
+ * The fields of the structure are discussed individually below:
+ *
+ * version: Integer field containing the version number of this version
+ *	of the H5C_image_ctl_t structure.  Any instance of
+ *	H5C_image_ctl_t passed to the cache must have a known
+ *	version number, or an error will be flagged.
+ *
+ * generate_image:  Boolean flag indicating whether a cache image should 
+ *	be created on file close.
+ *
+ * save_resize_status:  Boolean flag indicating whether the cache image 
+ *      should include the adaptive cache resize configuration and status.
+ *      Note that this field is ignored at present.
+ *
+ * entry_ageout:        Integer field indicating the maximum number of
+ *      times a prefetched entry can appear in subsequent cache images.
+ *      This field exists to allow the user to avoid the buildup of 
+ *      infrequently used entries in long sequences of cache images.
+ *
+ *      The value of this field must lie in the range
+ *      H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE (-1) to 
+ *      H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX (100).
+ *
+ *      H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE means that no limit  
+ *      is imposed on number of times a prefeteched entry can appear
+ *      in subsequent cache images.
+ *
+ *      A value of 0 prevents prefetched entries from being included 
+ *      in cache images.
+ *
+ *      Positive integers restrict prefetched entries to the specified
+ *      number of appearances.
+ *      
+ *      Note that the number of subsequent cache images that a prefetched
+ *      entry has appeared in is tracked in an 8 bit field.  Thus, while
+ *      H5AC__CACHE_IMAGE__ENTRY_AGEOUT__MAX can be increased from its  
+ *      current value, any value in excess of 255 will be the functional 
+ *      equivalent of H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE.
+ *
+ * flags: Unsigned integer containing flags controling which aspects of the
+ *	cache image functinality is actually executed.  The primary impetus 
+ *	behind this field is to allow developement of tests for partial 
+ *	implementations that will require little if any modification to run 
+ *	with the full implementation.  In normal operation, all flags should 
+ *	be set.
+ *
+ ****************************************************************************/
+
+#define H5C_CI__GEN_MDCI_SBE_MESG	((unsigned)0x0001)
+#define H5C_CI__GEN_MDC_IMAGE_BLK	((unsigned)0x0002)
+#define H5C_CI__SUPRESS_ENTRY_WRITES	((unsigned)0x0004)
+#define H5C_CI__WRITE_CACHE_IMAGE	((unsigned)0x0008)
+
+/* This #define must set all defined H5C_CI flags.  It is 
+ * used in the default value for instances of H5C_cache_image_ctl_t.
+ * This value will only be modified in test code.
+ */
+#define H5C_CI__ALL_FLAGS		((unsigned)0x000F)
+
+#define H5C__DEFAULT_CACHE_IMAGE_CTL                                  \
+{                                                                     \
+    /* version            = */ H5C__CURR_CACHE_IMAGE_CTL_VER,         \
+    /* generate_image     = */ FALSE,                                 \
+    /* save_resize_status = */ FALSE,                                 \
+    /* entry_ageout       = */ H5AC__CACHE_IMAGE__ENTRY_AGEOUT__NONE, \
+    /* flags              = */ H5C_CI__ALL_FLAGS                      \
+}
+
+typedef struct H5C_cache_image_ctl_t {
+    int32_t				version;
+    hbool_t				generate_image;
+    hbool_t                             save_resize_status;
+    int32_t                             entry_ageout;
+    unsigned				flags;
+} H5C_cache_image_ctl_t;
+
 /***************************************/
 /* Library-private Function Prototypes */
 /***************************************/
@@ -1770,6 +2217,8 @@ herr_t H5C_verify_tag(int id, haddr_t tag);
 H5_DLL herr_t H5C_flush_to_min_clean(H5F_t *f, hid_t dxpl_id);
 H5_DLL herr_t H5C_get_cache_auto_resize_config(const H5C_t *cache_ptr,
     H5C_auto_size_ctl_t *config_ptr);
+H5_DLL herr_t H5C_get_cache_image_config(const H5C_t * cache_ptr,
+    H5C_cache_image_ctl_t *config_ptr);
 H5_DLL herr_t H5C_get_cache_size(H5C_t *cache_ptr, size_t *max_size_ptr,
     size_t *min_clean_size_ptr, size_t *cur_size_ptr,
     uint32_t *cur_num_entries_ptr);
@@ -1783,8 +2232,11 @@ H5_DLL herr_t H5C_get_evictions_enabled(const H5C_t *cache_ptr, hbool_t *evictio
 H5_DLL void * H5C_get_aux_ptr(const H5C_t *cache_ptr);
 H5_DLL FILE *H5C_get_trace_file_ptr(const H5C_t *cache_ptr);
 H5_DLL FILE *H5C_get_trace_file_ptr_from_entry(const H5C_cache_entry_t *entry_ptr);
+H5_DLL herr_t H5C_image_stats(H5C_t * cache_ptr, hbool_t print_header);
 H5_DLL herr_t H5C_insert_entry(H5F_t *f, hid_t dxpl_id, const H5C_class_t *type,
     haddr_t addr, void *thing, unsigned int flags);
+H5_DLL herr_t H5C_load_cache_image_on_next_protect(H5F_t *f, haddr_t addr, 
+   hsize_t len, hbool_t rw);
 H5_DLL herr_t H5C_mark_entry_dirty(void *thing);
 H5_DLL herr_t H5C_mark_entry_clean(void *thing);
 H5_DLL herr_t H5C_mark_entry_unserialized(void *thing);
@@ -1799,6 +2251,8 @@ H5_DLL void * H5C_protect(H5F_t *f, hid_t dxpl_id, const H5C_class_t *type,
 H5_DLL herr_t H5C_reset_cache_hit_rate_stats(H5C_t *cache_ptr);
 H5_DLL herr_t H5C_resize_entry(void *thing, size_t new_size);
 H5_DLL herr_t H5C_set_cache_auto_resize_config(H5C_t *cache_ptr, H5C_auto_size_ctl_t *config_ptr);
+H5_DLL herr_t H5C_set_cache_image_config(const H5F_t *f, H5C_t *cache_ptr,
+    H5C_cache_image_ctl_t *config_ptr);
 H5_DLL herr_t H5C_set_evictions_enabled(H5C_t *cache_ptr, hbool_t evictions_enabled);
 H5_DLL herr_t H5C_set_prefix(H5C_t *cache_ptr, char *prefix);
 H5_DLL herr_t H5C_set_trace_file_ptr(H5C_t *cache_ptr, FILE *trace_file_ptr);
@@ -1810,6 +2264,7 @@ H5_DLL herr_t H5C_unpin_entry(void *thing);
 H5_DLL herr_t H5C_destroy_flush_dependency(void *parent_thing, void *child_thing);
 H5_DLL herr_t H5C_unprotect(H5F_t *f, hid_t dxpl_id, haddr_t addr, void *thing,
     unsigned int flags);
+H5_DLL herr_t H5C_validate_cache_image_config(H5C_cache_image_ctl_t * ctl_ptr);
 H5_DLL herr_t H5C_validate_resize_config(H5C_auto_size_ctl_t *config_ptr,
     unsigned int tests);
 H5_DLL herr_t H5C_ignore_tags(H5C_t *cache_ptr);
@@ -1819,6 +2274,8 @@ H5_DLL herr_t H5C_cork(H5C_t *cache_ptr, haddr_t obj_addr, unsigned action, hboo
 H5_DLL herr_t H5C_get_entry_ring(const H5F_t *f, haddr_t addr, H5C_ring_t *ring);
 H5_DLL herr_t H5C_unsettle_entry_ring(void *thing);
 H5_DLL herr_t H5C_remove_entry(void *thing);
+H5_DLL herr_t H5C_cache_image_status(H5F_t * f, hbool_t *load_ci_ptr, 
+    hbool_t *write_ci_ptr);
 
 #ifdef H5_HAVE_PARALLEL
 H5_DLL herr_t H5C_apply_candidate_list(H5F_t *f, hid_t dxpl_id,
@@ -1832,7 +2289,16 @@ H5_DLL herr_t H5C_mark_entries_as_clean(H5F_t *f, hid_t dxpl_id, int32_t ce_arra
 #endif /* H5_HAVE_PARALLEL */
 
 #ifndef NDEBUG	/* debugging functions */
+H5_DLL hbool_t H5C_get_serialization_in_progress(const H5C_t *cache_ptr);
 H5_DLL hbool_t H5C_cache_is_clean(const H5C_t *cache_ptr, H5C_ring_t inner_ring);
+H5_DLL herr_t H5C_get_entry_ptr_from_addr(H5C_t *cache_ptr, haddr_t addr,
+    void **entry_ptr_ptr);
+H5_DLL herr_t H5C_flush_dependency_exists(H5C_t *cache_ptr, haddr_t parent_addr, 
+    haddr_t child_addr, hbool_t *fd_exists_ptr);
+H5_DLL herr_t H5C_verify_entry_type(H5C_t *cache_ptr, haddr_t addr,
+    const H5C_class_t *expected_type, hbool_t *in_cache_ptr,
+    hbool_t *type_ok_ptr);
+H5_DLL herr_t H5C_validate_index_list(H5C_t *cache_ptr);
 #endif /* NDEBUG */
 
 #endif /* !_H5Cprivate_H */
diff --git a/src/H5F.c b/src/H5F.c
index fc36da1..d3e365a 100644
--- a/src/H5F.c
+++ b/src/H5F.c
@@ -445,6 +445,8 @@ done:
 hid_t
 H5Fcreate(const char *filename, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
 {
+    hbool_t      ci_load = FALSE;       /* whether MDC ci load requested */
+    hbool_t      ci_write = FALSE;      /* whether MDC CI write requested */
     H5F_t	*new_file = NULL;	/*file struct for new file	*/
     hid_t        dxpl_id = H5AC_ind_read_dxpl_id; /*dxpl used by library        */
     hid_t	 ret_value;	        /*return value			*/
@@ -490,6 +492,14 @@ H5Fcreate(const char *filename, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     if(NULL == (new_file = H5F_open(filename, flags, fcpl_id, fapl_id, dxpl_id)))
         HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to create file")
 
+   /* check to see if both SWMR and cache image are requested.  Fail if so */
+   if ( H5C_cache_image_status(new_file, &ci_load, &ci_write) < 0 )
+       HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "can't get MDC CI status")
+
+   if ( ( ( ci_load ) || ( ci_write ) ) &&
+        ( flags & (H5F_ACC_SWMR_READ | H5F_ACC_SWMR_WRITE) ) )
+       HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "can't have both SWMR and cache image.")
+
     /* Get an atom for the file */
     if((ret_value = H5I_register(H5I_FILE, new_file, TRUE)) < 0)
         HGOTO_ERROR(H5E_ATOM, H5E_CANTREGISTER, FAIL, "unable to atomize file")
@@ -498,9 +508,29 @@ H5Fcreate(const char *filename, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     new_file->file_id = ret_value;
 
 done:
+#if 0
+    /* Quincy: please review this.  With the original cleanup code (below)
+     * my code (above) to disable the combination of SWMR and cache image,
+     * triggering results in an assertion failure in H5F_close() either 
+     * immediately or on library shutdown depending on the exact location 
+     * of my code.
+     *
+     * I noticed that the issue did not appear in H5Fopen().  As that function 
+     * calls H5F_try_close() instead of H5F_close(), I tried copying that 
+     * cleanup code here.  It seems to work -- but since I'm not familiar
+     * with this section of the code, it would be good if you would check me.
+     *
+     * Please delete the old version if you buy the fix.
+     *
+     *                                           JRM -- 12/29/16
+     */
     if(ret_value < 0 && new_file)
         if(H5F_close(new_file) < 0)
             HDONE_ERROR(H5E_FILE, H5E_CANTCLOSEFILE, FAIL, "problems closing file")
+#else
+    if(ret_value < 0 && new_file && H5F_try_close(new_file, NULL) < 0)
+        HDONE_ERROR(H5E_FILE, H5E_CANTCLOSEFILE, FAIL, "problems closing file")
+#endif
 
     FUNC_LEAVE_API(ret_value)
 } /* end H5Fcreate() */
@@ -549,6 +579,8 @@ done:
 hid_t
 H5Fopen(const char *filename, unsigned flags, hid_t fapl_id)
 {
+    hbool_t      ci_load = FALSE;       /* whether MDC ci load requested */
+    hbool_t      ci_write = FALSE;      /* whether MDC CI write requested */
     H5F_t	*new_file = NULL;	/*file struct for new file	*/
     hid_t        dxpl_id = H5AC_ind_read_dxpl_id; /*dxpl used by library        */
     hid_t	 ret_value;	        /*return value			*/
@@ -578,6 +610,14 @@ H5Fopen(const char *filename, unsigned flags, hid_t fapl_id)
     if(NULL == (new_file = H5F_open(filename, flags, H5P_FILE_CREATE_DEFAULT, fapl_id, dxpl_id)))
         HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "unable to open file")
 
+    /* check to see if both SWMR and cache image are requested.  Fail if so */
+    if ( H5C_cache_image_status(new_file, &ci_load, &ci_write) < 0 )
+        HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "can't get MDC CI status")
+
+    if ( ( ( ci_load ) || ( ci_write ) ) &&
+         ( flags & (H5F_ACC_SWMR_READ | H5F_ACC_SWMR_WRITE) ) )
+        HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL, "can't have both SWMR and cache image")
+
     /* Get an atom for the file */
     if((ret_value = H5I_register(H5I_FILE, new_file, TRUE)) < 0)
         HGOTO_ERROR(H5E_ATOM, H5E_CANTREGISTER, FAIL, "unable to atomize file handle")
@@ -1593,6 +1633,8 @@ done:
 herr_t
 H5Fstart_swmr_write(hid_t file_id)
 {
+    hbool_t ci_load = FALSE;    /* whether MDC ci load requested */
+    hbool_t ci_write = FALSE;   /* whether MDC CI write requested */
     H5F_t *file = NULL;         /* File info */
     size_t grp_dset_count=0; 	/* # of open objects: groups & datasets */
     size_t nt_attr_count=0; 	/* # of opened named datatypes  + opened attributes */
@@ -1626,6 +1668,13 @@ H5Fstart_swmr_write(hid_t file_id)
 
     HDassert(file->shared->sblock->status_flags & H5F_SUPER_WRITE_ACCESS);
 
+    /* check to see if cache image is enabled.  Fail if so */
+    if ( H5C_cache_image_status(file, &ci_load, &ci_write) < 0 )
+        HGOTO_ERROR(H5E_FILE, H5E_BADVALUE, FAIL, "can't get MDC CI status")
+
+    if ( ( ci_load ) || ( ci_write ) )
+        HGOTO_ERROR(H5E_FILE, H5E_BADVALUE, FAIL, "can't have both SWMR and MDC cache image.")
+
     /* Flush data buffers */
     if(H5F_flush(file, H5AC_ind_read_dxpl_id, FALSE) < 0)
         HGOTO_ERROR(H5E_FILE, H5E_CANTFLUSH, FAIL, "unable to flush file's cached information")
@@ -1868,7 +1917,48 @@ H5Fget_mdc_logging_status(hid_t file_id, hbool_t *is_enabled,
 
 done:
     FUNC_LEAVE_API(ret_value)
-} /* H5Fstop_mdc_logging() */
+} /* H5Fget_mdc_logging_status() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:   H5Fset_latest_format
+ *
+ * Purpose:    Enable switching the "latest format" flag while a file is open.
+ *
+ * Return:     Non-negative on success/Negative on failure
+ *
+ * Programmer: Quincey Koziol
+ *             Monday, September 21, 2015
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Fset_latest_format(hid_t file_id, hbool_t latest_format)
+{
+    H5F_t *f;                           /* File */
+    unsigned latest_flags;              /* Latest format flags for file */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "ib", file_id, latest_format);
+
+    /* Check args */
+    if(NULL == (f = (H5F_t *)H5I_object_verify(file_id, H5I_FILE)))
+        HGOTO_ERROR(H5E_FILE, H5E_BADVALUE, FAIL, "not a file ID")
+
+    /* Check if the value is changing */
+    latest_flags = H5F_USE_LATEST_FLAGS(f, H5F_LATEST_ALL_FLAGS);
+    if(latest_format != (H5F_LATEST_ALL_FLAGS == latest_flags)) {
+        /* Call the flush routine, for this file */
+        if(H5F_flush(f, H5AC_ind_read_dxpl_id, FALSE) < 0)
+            HGOTO_ERROR(H5E_FILE, H5E_CANTFLUSH, FAIL, "unable to flush file's cached information")
+
+        /* Toggle the 'latest format' flag */
+        H5F_SET_LATEST_FLAGS(f, latest_format ? H5F_LATEST_ALL_FLAGS : 0);
+    } /* end if */
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Fset_latest_format() */
 
 
 /*-------------------------------------------------------------------------
diff --git a/src/H5Fint.c b/src/H5Fint.c
index 8ad97a8..4783a36 100644
--- a/src/H5Fint.c
+++ b/src/H5Fint.c
@@ -188,6 +188,8 @@ H5F_get_access_plist(H5F_t *f, hbool_t app_ref)
     if(H5P_set(new_plist, H5F_ACS_COLL_MD_WRITE_FLAG_NAME, &(f->coll_md_write)) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't set collective metadata read flag")
 #endif /* H5_HAVE_PARALLEL */
+    if(H5P_set(new_plist, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_NAME, &(f->shared->mdc_initCacheImageCfg)) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set initial metadata cache resize config.")
 
     /* Prepare the driver property */
     driver_prop.driver_id = f->shared->lf->driver_id;
@@ -667,6 +669,8 @@ H5F_new(H5F_file_t *shared, unsigned flags, hid_t fcpl_id, hid_t fapl_id, H5FD_t
         if(H5P_get(plist, H5F_ACS_COLL_MD_WRITE_FLAG_NAME, &(f->coll_md_write)) < 0)
             HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get collective metadata write flag")
 #endif /* H5_HAVE_PARALLEL */
+        if(H5P_get(plist, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_NAME, &(f->shared->mdc_initCacheImageCfg)) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't get initial metadata cache resize config")
 
         /* Get the VFD values to cache */
         f->shared->maxaddr = H5FD_get_maxaddr(lf);
@@ -750,7 +754,7 @@ H5F_new(H5F_file_t *shared, unsigned flags, hid_t fcpl_id, hid_t fapl_id, H5FD_t
          * The cache might be created with a different number of elements and
          * the access property list should be updated to reflect that.
          */
-        if(H5AC_create(f, &(f->shared->mdc_initCacheCfg)) < 0)
+        if(H5AC_create(f, &(f->shared->mdc_initCacheCfg), &(f->shared->mdc_initCacheImageCfg)) < 0)
             HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to create metadata cache")
 
         /* Create the file's "open object" information */
@@ -2671,3 +2675,33 @@ H5F_set_coll_md_read(H5F_t *f, H5P_coll_md_read_flag_t cmr)
 } /* H5F_set_coll_md_read() */
 #endif /* H5_HAVE_PARALLEL */
 
+
+/*-------------------------------------------------------------------------
+ * Function:    H5F_set_latest_flags
+ *
+ * Purpose:     Set the latest_flags field with a new value.
+ *
+ * Return:      Success:        SUCCEED
+ *              Failure:        FAIL
+ *
+ * Programmer:  Quincey Koziol
+ *              4/26/16
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5F_set_latest_flags(H5F_t *f, unsigned flags)
+{
+    /* Use FUNC_ENTER_NOAPI_NOINIT_NOERR here to avoid performance issues */
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    /* Sanity check */
+    HDassert(f);
+    HDassert(f->shared);
+    HDassert(0 == ((~flags) & H5F_LATEST_ALL_FLAGS));
+
+    f->shared->latest_flags = flags;
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* H5F_set_latest_flags() */
+
diff --git a/src/H5Fpkg.h b/src/H5Fpkg.h
index c067f26..93a3978 100644
--- a/src/H5Fpkg.h
+++ b/src/H5Fpkg.h
@@ -287,6 +287,12 @@ struct H5F_file_t {
                                 /* metadata cache.  This structure is   */
                                 /* fixed at creation time and should    */
                                 /* not change thereafter.               */
+    H5AC_cache_image_config_t 
+		mdc_initCacheImageCfg;  /* initial configuration for the */
+                                        /* generate metadata cache image on     */
+                                        /* close option.  This structure is     */
+                                        /* fixed at creation time and should    */
+                                        /* not change thereafter.               */
     hbool_t     use_mdc_logging; /* Set when metadata logging is desired */
     hbool_t     start_mdc_log_on_access; /* set when mdc logging should  */
                                 /* begin on file access/create          */
@@ -397,7 +403,8 @@ H5_DLL herr_t H5F__super_free(H5F_super_t *sblock);
 
 /* Superblock extension related routines */
 H5_DLL herr_t H5F_super_ext_open(H5F_t *f, haddr_t ext_addr, H5O_loc_t *ext_ptr);
-H5_DLL herr_t H5F_super_ext_write_msg(H5F_t *f, hid_t dxpl_id, unsigned id, void *mesg, hbool_t may_create);
+H5_DLL herr_t H5F_super_ext_write_msg(H5F_t *f, hid_t dxpl_id, unsigned id,
+    void *mesg, hbool_t may_create, unsigned mesg_flags);
 H5_DLL herr_t H5F_super_ext_remove_msg(H5F_t *f, hid_t dxpl_id, unsigned id);
 H5_DLL herr_t H5F_super_ext_close(H5F_t *f, H5O_loc_t *ext_ptr, hid_t dxpl_id,
     hbool_t was_created);
diff --git a/src/H5Fprivate.h b/src/H5Fprivate.h
index bcc56c6..7d288fa 100644
--- a/src/H5Fprivate.h
+++ b/src/H5Fprivate.h
@@ -317,6 +317,7 @@
 #define H5F_SET_GRP_BTREE_SHARED(F, RC) (((F)->shared->grp_btree_shared = (RC)) ? SUCCEED : FAIL)
 #define H5F_USE_TMP_SPACE(F)    ((F)->shared->use_tmp_space)
 #define H5F_IS_TMP_ADDR(F, ADDR) (H5F_addr_le((F)->shared->tmp_addr, (ADDR)))
+#define H5F_SET_LATEST_FLAGS(F, FL)  ((F)->shared->latest_flags = (FL))
 #ifdef H5_HAVE_PARALLEL
 #define H5F_COLL_MD_READ(F)     ((F)->coll_md_read)
 #endif /* H5_HAVE_PARALLEL */
@@ -367,6 +368,7 @@
 #define H5F_SET_GRP_BTREE_SHARED(F, RC) (H5F_set_grp_btree_shared((F), (RC)))
 #define H5F_USE_TMP_SPACE(F)    (H5F_use_tmp_space(F))
 #define H5F_IS_TMP_ADDR(F, ADDR) (H5F_is_tmp_addr((F), (ADDR)))
+#define H5F_SET_LATEST_FLAGS(F, FL)  (H5F_set_latest_flags((F), (FL)))
 #ifdef H5_HAVE_PARALLEL
 #define H5F_COLL_MD_READ(F)     (H5F_coll_md_read(F))
 #endif /* H5_HAVE_PARALLEL */
@@ -481,6 +483,7 @@
 #define H5F_ACS_EVICT_ON_CLOSE_FLAG_NAME        "evict_on_close_flag" /* Whether or not the metadata cache will evict objects on close */
 #define H5F_ACS_CORE_WRITE_TRACKING_PAGE_SIZE_NAME "core_write_tracking_page_size" /* The page size in kiB when core VFD write tracking is enabled */
 #define H5F_ACS_COLL_MD_WRITE_FLAG_NAME         "collective_metadata_write" /* property indicating whether metadata writes are done collectively or not */
+#define H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_NAME "mdc_initCacheImageCfg" /* Initial metadata cache image creation configuration */
 
 /* ======================== File Mount properties ====================*/
 #define H5F_MNT_SYM_LOCAL_NAME 		"local"                 /* Whether absolute symlinks local to file. */
@@ -700,6 +703,7 @@ H5_DLL struct H5UC_t *H5F_grp_btree_shared(const H5F_t *f);
 H5_DLL herr_t H5F_set_grp_btree_shared(H5F_t *f, struct H5UC_t *rc);
 H5_DLL hbool_t H5F_use_tmp_space(const H5F_t *f);
 H5_DLL hbool_t H5F_is_tmp_addr(const H5F_t *f, haddr_t addr);
+H5_DLL herr_t H5F_set_latest_flags(H5F_t *f, unsigned flags);
 #ifdef H5_HAVE_PARALLEL
 H5_DLL H5P_coll_md_read_flag_t H5F_coll_md_read(const H5F_t *f);
 H5_DLL void H5F_set_coll_md_read(H5F_t *f, H5P_coll_md_read_flag_t flag);
diff --git a/src/H5Fpublic.h b/src/H5Fpublic.h
index a79da75..c57a821 100644
--- a/src/H5Fpublic.h
+++ b/src/H5Fpublic.h
@@ -246,6 +246,7 @@ H5_DLL herr_t H5Fstart_swmr_write(hid_t file_id);
 H5_DLL ssize_t H5Fget_free_sections(hid_t file_id, H5F_mem_t type,
     size_t nsects, H5F_sect_info_t *sect_info/*out*/);
 H5_DLL herr_t H5Fclear_elink_file_cache(hid_t file_id);
+H5_DLL herr_t H5Fset_latest_format(hid_t file_id, hbool_t latest_format);
 H5_DLL herr_t H5Fstart_mdc_logging(hid_t file_id);
 H5_DLL herr_t H5Fstop_mdc_logging(hid_t file_id);
 H5_DLL herr_t H5Fget_mdc_logging_status(hid_t file_id,
diff --git a/src/H5Fsuper.c b/src/H5Fsuper.c
index 893ce26..e203c38 100644
--- a/src/H5Fsuper.c
+++ b/src/H5Fsuper.c
@@ -290,7 +290,7 @@ H5F__update_super_ext_driver_msg(H5F_t *f, hid_t dxpl_id)
                      */
                     drvinfo.len = driver_size;
                     drvinfo.buf = dbuf;
-                    if(H5F_super_ext_write_msg(f, dxpl_id, H5O_DRVINFO_ID, &drvinfo, FALSE) < 0)
+                    if(H5F_super_ext_write_msg(f, dxpl_id, H5O_DRVINFO_ID, &drvinfo, FALSE, H5O_MSG_NO_FLAGS_SET) < 0)
                         HGOTO_ERROR(H5E_FILE, H5E_WRITEERROR, FAIL, "unable to update driver info header message")
                 } /* end if driver_size > 0 */
             } /* end if !H5F_HAS_FEATURE(f, H5FD_FEAT_IGNORE_DRVRINFO) */
@@ -692,6 +692,34 @@ H5F__super_read(H5F_t *f, hid_t dxpl_id, hbool_t initial_read)
 		f->shared->fs_addr[u] = fsinfo.fs_addr[u-1];
         } /* end if */
 
+	/* Check for the extension having a 'metadata cache image' message */
+        if((status = H5O_msg_exists(&ext_loc, H5O_MDCI_MSG_ID, dxpl_id)) < 0)
+            HGOTO_ERROR(H5E_FILE, H5E_EXISTS, FAIL, "unable to read object header")
+        if(status) {
+            hbool_t 	rw = ((rw_flags & H5AC__READ_ONLY_FLAG) == 0);
+	    H5O_mdci_t  mdci_msg;
+
+	    /* if the metadata cache image superblock extension message exists,
+             * read its contents and pass the data on to the metadata cache.
+             * Given this data, the cache will load and decode the metadata
+ 	     * cache image block, decoded it and load its contents into the 
+	     * the cache on the test protect call.  
+             *
+             * Further, if the file is opened R/W, the metadata cache will 
+	     * delete the metadata cache image superblock extension and free
+	     * the cache image block.  Don't do this now as f->shared 
+	     * is not fully setup, which complicates matters.
+             */
+
+            /* Retrieve the 'metadata cache image message' structure */
+	    if(NULL == H5O_msg_read(&ext_loc, H5O_MDCI_MSG_ID, &mdci_msg, dxpl_id))
+                HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "unable to get metadata cache image message")
+
+            /* Indicate to the cache that there's an image to load on first protect call */
+            if(H5AC_load_cache_image_on_next_protect(f, mdci_msg.addr, mdci_msg.size, rw) < 0)
+		HGOTO_ERROR(H5E_FILE, H5E_CANTLOAD, FAIL, "call to H5AC_load_cache_image_on_next_protect failed");
+        } /* end if */
+
         /* Close superblock extension */
         if(H5F_super_ext_close(f, &ext_loc, dxpl_id, FALSE) < 0)
 	    HGOTO_ERROR(H5E_FILE, H5E_CANTCLOSEOBJ, FAIL, "unable to close file's superblock extension")
@@ -737,7 +765,7 @@ H5F__super_read(H5F_t *f, hid_t dxpl_id, hbool_t initial_read)
 		HDassert(f->shared->sblock == NULL);
 		f->shared->sblock = sblock;
 #endif /* JRM */
-		if(H5F_super_ext_write_msg(f, dxpl_id, H5O_DRVINFO_ID, &drvinfo, FALSE) < 0)
+		if(H5F_super_ext_write_msg(f, dxpl_id, H5O_DRVINFO_ID, &drvinfo, FALSE, H5O_MSG_NO_FLAGS_SET) < 0)
                     HGOTO_ERROR(H5E_FILE, H5E_WRITEERROR, FAIL, "error in writing message to superblock extension")
 
 #if 1 /* bug fix test code -- tidy this up if all goes well */ /* JRM */
@@ -1365,7 +1393,8 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5F_super_ext_write_msg(H5F_t *f, hid_t dxpl_id, unsigned id, void *mesg, hbool_t may_create)
+H5F_super_ext_write_msg(H5F_t *f, hid_t dxpl_id, unsigned id, void *mesg,
+    hbool_t may_create, unsigned mesg_flags)
 {
     H5P_genplist_t *dxpl = NULL;        /* DXPL for setting ring */
     H5AC_ring_t orig_ring = H5AC_RING_INV;      /* Original ring value */
@@ -1410,7 +1439,7 @@ H5F_super_ext_write_msg(H5F_t *f, hid_t dxpl_id, unsigned id, void *mesg, hbool_
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "Message should not exist")
 
 	/* Create the message with ID in the superblock extension */
-	if(H5O_msg_create(&ext_loc, id, H5O_MSG_FLAG_DONTSHARE, H5O_UPDATE_TIME, mesg, dxpl_id) < 0)
+	if(H5O_msg_create(&ext_loc, id, (mesg_flags | H5O_MSG_FLAG_DONTSHARE), H5O_UPDATE_TIME, mesg, dxpl_id) < 0)
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "unable to create the message in object header")
     } /* end if */
     else {
@@ -1418,7 +1447,7 @@ H5F_super_ext_write_msg(H5F_t *f, hid_t dxpl_id, unsigned id, void *mesg, hbool_
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "Message should exist")
 
 	/* Update the message with ID in the superblock extension */
-	if(H5O_msg_write(&ext_loc, id, H5O_MSG_FLAG_DONTSHARE, H5O_UPDATE_TIME, mesg, dxpl_id) < 0)
+	if(H5O_msg_write(&ext_loc, id, (mesg_flags | H5O_MSG_FLAG_DONTSHARE), H5O_UPDATE_TIME, mesg, dxpl_id) < 0)
 	    HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "unable to write the message in object header")
     } /* end else */
 
diff --git a/src/H5HFcache.c b/src/H5HFcache.c
index 302fe04..8e5ed76 100644
--- a/src/H5HFcache.c
+++ b/src/H5HFcache.c
@@ -116,14 +116,17 @@ static herr_t H5HF__cache_dblock_free_icr(void *thing);
 
 /* Debugging Function Prototypes */
 #ifndef NDEBUG
-static herr_t H5HF__cache_verify_hdr_descendants_clean(H5F_t *f, H5HF_hdr_t *hdr,
-    hbool_t *clean);
-static herr_t H5HF__cache_verify_iblock_descendants_clean(H5F_t *f,
-    H5HF_indirect_t *iblock, unsigned *iblock_status, hbool_t *clean);
-static herr_t H5HF__cache_verify_iblocks_dblocks_clean(H5F_t *f,
-    H5HF_indirect_t *iblock, hbool_t *clean, hbool_t *has_dblocks);
-static herr_t H5HF__cache_verify_descendant_iblocks_clean(H5F_t *f,
-    H5HF_indirect_t *iblock, hbool_t *clean, hbool_t *has_iblocks);
+static herr_t H5HF__cache_verify_hdr_descendants_clean(H5F_t *f, hid_t dxpl_id,
+    H5HF_hdr_t * hdr, hbool_t *fd_clean, hbool_t *clean);
+static herr_t H5HF__cache_verify_iblock_descendants_clean(H5F_t *f, 
+    hid_t dxpl_id, haddr_t fd_parent_addr, H5HF_indirect_t *iblock, 
+    unsigned *iblock_status, hbool_t * fd_clean, hbool_t *clean);
+static herr_t H5HF__cache_verify_iblocks_dblocks_clean(H5F_t *f, 
+    haddr_t fd_parent_addr, H5HF_indirect_t *iblock, hbool_t *fd_clean, 
+    hbool_t *clean, hbool_t *has_dblocks);
+static herr_t H5HF__cache_verify_descendant_iblocks_clean(H5F_t *f, 
+    hid_t dxpl_id, haddr_t fd_parent_addr, H5HF_indirect_t *iblock, 
+    hbool_t *fd_clean, hbool_t *clean, hbool_t *has_iblocks);
 #endif /* NDEBUG */
 
 
@@ -687,6 +690,7 @@ H5HF__cache_hdr_pre_serialize(H5F_t *f, hid_t H5_ATTR_UNUSED dxpl_id,
 #ifndef NDEBUG
 {
     hbool_t descendants_clean = TRUE;
+    hbool_t fd_children_clean = TRUE;
 
     /* Verify that flush dependencies are working correctly.  Do this
      * by verifying that either:
@@ -701,10 +705,22 @@ H5HF__cache_hdr_pre_serialize(H5F_t *f, hid_t H5_ATTR_UNUSED dxpl_id,
      *    constraint is met by default.
      *
      * Do this with a call to H5HF__cache_verify_hdr_descendants_clean().
+     *
+     * Note that decendants need not be clean if the pre_serialize call
+     * is made during a cache serialization instead of an entry or cache
+     * flush.
+     *
+     * Note also that with the recent change in the definition of flush 
+     * dependency, not all decendants need be clean -- only direct flush 
+     * dependency children.
+     *
+     * Finally, observe that the H5HF__cache_verify_hdr_descendants_clean()
+     * call still looks for dirty descendants.  At present we do not check
+     * this value.
      */
-    if(H5HF__cache_verify_hdr_descendants_clean((H5F_t *)f, hdr, &descendants_clean) < 0)
+    if(H5HF__cache_verify_hdr_descendants_clean((H5F_t *)f, dxpl_id, hdr, &fd_children_clean, &descendants_clean) < 0)
          HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "can't verify hdr descendants clean.")
-    HDassert(descendants_clean);
+    HDassert(fd_children_clean);
 }
 #endif /* NDEBUG */
 
@@ -1176,8 +1192,9 @@ H5HF__cache_iblock_image_len(const void *_thing, size_t *image_len)
  *		and if so, to move it to real file space before the entry is 
  *		serialized.
  *
- *		In debug compiles, this function also verifies that all children
- *		of this indirect block are either clean or are not in cache.
+ *		In debug compiles, this function also verifies that all 
+ *		immediate flush dependency children of this indirect block 
+ *		are either clean or are not in cache.
  *
  * Return:	Success:	SUCCEED
  *		Failure:	FAIL
@@ -1217,10 +1234,12 @@ H5HF__cache_iblock_pre_serialize(H5F_t *f, hid_t dxpl_id, void *_thing,
 #ifndef NDEBUG
 {
     hbool_t 		 descendants_clean = TRUE;
+    hbool_t		 fd_children_clean = TRUE;
     unsigned 		 iblock_status = 0;
 
     /* verify that flush dependencies are working correctly.  Do this
-     * by verifying that all children of this iblock are clean.
+     * by verifying that all immediate flush dependency children of this 
+     * iblock are clean.
      */
     if(H5AC_get_entry_status(f, iblock->addr, &iblock_status) < 0)
         HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't get iblock status")
@@ -1230,9 +1249,9 @@ H5HF__cache_iblock_pre_serialize(H5F_t *f, hid_t dxpl_id, void *_thing,
      * there is no need to check to see if it is pinned or protected, or to
      * protect it if it is not.
      */
-    if(H5HF__cache_verify_iblock_descendants_clean((H5F_t *)f, iblock, &iblock_status, &descendants_clean) < 0)
+    if(H5HF__cache_verify_iblock_descendants_clean((H5F_t *)f, dxpl_id, iblock->addr, iblock, &iblock_status, &fd_children_clean, &descendants_clean) < 0)
          HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "can't verify descendants clean.")
-    HDassert(descendants_clean);
+    HDassert(fd_children_clean);
 }
 #endif /* NDEBUG */
 
@@ -2585,6 +2604,54 @@ done:
  *		instance of H5HF_hdr_t are clean.  Set *clean to 
  *		TRUE if this is the case, and to FALSE otherwise.
  *
+ *		Update -- 8/24/15
+ *
+ *		With the advent of the metadata cache image feature, it is
+ *		possible for the pre-serialize and serialize calls to be
+ *		invoked outside of a flush.  While this serialization
+ *		observes flush dependencies for the order of serialization,
+ *		the entries are not written to disk, and hence dirty entries
+ *		remain dirty.
+ *
+ *		To address this, updated the sanity checks in this function
+ *		to treat entries whose images are up to date as clean if 
+ *		a cache serialization is in progress.
+ *
+ *		Update -- 9/29/16
+ *
+ *		The implementation of flush dependencies has been changed.
+ *		Prior to this change, a flush dependency parent could be 
+ *		flushed if and only if all its flush dependency decendants
+ *		were clean.  In the new definition, a flush dependency 
+ *		parent can be flushed if all its immediate flush dependency
+ *		children are clean, regardless of any other dirty 
+ *		decendants.  
+ *
+ *		Further, metadata cache entries are now allowed to have 
+ *		multiple flush dependency parents.  
+ *
+ *		This means that the fractal heap is no longer ncessarily 
+ *		flushed from the bottom up.
+ *
+ *		For example, it is now possible for a dirty fractal heap 
+ *		header to be flushed before a dirty dblock, as long as the
+ *		there in an interviening iblock, and the header has no 
+ *		dirty immediate flush dependency children.
+ *
+ *		Also, I gather that under some circumstances, a dblock 
+ *		will be direct a flush dependency child both of the iblock 
+ *		that points to it, and of the fractal heap header.
+ *
+ *		As a result of these changes, the functionality of these
+ *		sanity checking routines has been modified significantly.
+ *		Instead of scanning the fractal heap from a starting point
+ *		down, and verifying that there were no dirty entries, the 
+ *		functions now scan downward from the starting point and 
+ *		verify that there are no dirty flush dependency children 
+ *		of the specified flush dependency parent.  In passing, 
+ *		they also walk the data structure, and verify it.
+ *
+ *
  * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:	John Mainzer
@@ -2594,9 +2661,10 @@ done:
  */
 #ifndef NDEBUG
 static herr_t
-H5HF__cache_verify_hdr_descendants_clean(H5F_t *f, H5HF_hdr_t *hdr,
-    hbool_t *clean)
+H5HF__cache_verify_hdr_descendants_clean(H5F_t *f, hid_t dxpl_id,
+    H5HF_hdr_t *hdr, hbool_t *fd_clean, hbool_t *clean)
 {
+    hbool_t     fd_exists = FALSE;      /* whether flush dependency exists. */
     haddr_t	hdr_addr;               /* Address of header */
     unsigned	hdr_status = 0;         /* Header cache entry status */
     herr_t      ret_value = SUCCEED;    /* Return value */
@@ -2608,6 +2676,7 @@ H5HF__cache_verify_hdr_descendants_clean(H5F_t *f, H5HF_hdr_t *hdr,
     HDassert(hdr);
     HDassert(hdr->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
     HDassert(hdr->cache_info.type == H5AC_FHEAP_HDR);
+    HDassert(fd_clean);
     HDassert(clean);
     hdr_addr = hdr->cache_info.addr;
     HDassert(hdr_addr == hdr->heap_addr);
@@ -2672,15 +2741,165 @@ H5HF__cache_verify_hdr_descendants_clean(H5F_t *f, H5HF_hdr_t *hdr,
 	root_iblock_in_cache = ( (root_iblock_status & H5AC_ES__IN_CACHE) != 0);
 	HDassert(root_iblock_in_cache || (root_iblock == NULL));
 
-	if(!root_iblock_in_cache) /* we are done */
-	    *clean = TRUE;
-	else if(root_iblock_status & H5AC_ES__IS_DIRTY)
-	    *clean = FALSE;
+        if(!root_iblock_in_cache) { /* we are done */
+            *clean = TRUE;
+            *fd_clean = TRUE;
+        } /* end if */
+        else if((root_iblock_status & H5AC_ES__IS_DIRTY) &&
+                  (((root_iblock_status & H5AC_ES__IMAGE_IS_UP_TO_DATE) == 0) ||
+                   (!H5AC_get_serialization_in_progress(f)))) {
+            *clean = FALSE;
+
+            /* verify that a flush dependency exists between the header and
+             * the root inode.
+             */
+            if(H5AC_flush_dependency_exists(f, hdr->heap_addr, root_iblock_addr, &fd_exists) < 0)
+                HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check flush dependency")
+            HDassert(fd_exists);
+
+            *fd_clean = FALSE;
+        } /* end else-if */
+        else { /* must examine children */
+            hbool_t     unprotect_root_iblock = FALSE;
+
+            /* At this point, the root iblock may be pinned, protected,
+             * both, or neither, and we may or may not have a pointer
+             * to root iblock in memory.  
+             *
+             * Before we call H5HF__cache_verify_iblock_descendants_clean(),
+             * we must ensure that the root iblock is either pinned or 
+             * protected or both, and that we have a pointer to it.  
+             * Do this as follows:
+             */
+            if(root_iblock == NULL) {   /* we don't have ptr to root iblock */
+                if(0 == (root_iblock_status & H5AC_ES__IS_PROTECTED)) {
+                    /* just protect the root iblock -- this will give us
+                     * the pointer we need to proceed, and ensure that 
+                     * it is locked into the metadata cache for the 
+                     * duration.
+                     *
+                     * Note that the udata is only used in the load callback.
+                     * While the fractal heap makes heavy use of the udata
+                     * in this case, since we know that the entry is in cache,
+                     * we can pass NULL udata.
+                     *
+                     * The tag specified in the dxpl we received
+                     * as a parameter (via dxpl_id) may not be correct.
+                     * Grab the (hopefully) correct tag from the header,
+                     * and load it into the dxpl via the H5_BEGIN_TAG and 
+                     * H5_END_TAG macros.  Note that any error bracked by
+                     * these macros must be reported with HGOTO_ERROR_TAG. 
+                     */
+                    H5_BEGIN_TAG(dxpl_id, hdr->heap_addr, FAIL)
+
+                    if(NULL == (root_iblock = (H5HF_indirect_t *)H5AC_protect(f, dxpl_id, H5AC_FHEAP_IBLOCK, root_iblock_addr, NULL, H5AC__READ_ONLY_FLAG)))
+                        HGOTO_ERROR_TAG(H5E_HEAP, H5E_CANTPROTECT, FAIL, "H5AC_protect() faild.")
+
+                    H5_END_TAG(FAIL)
+
+                    unprotect_root_iblock = TRUE;
+                } /* end if */
+                else {
+                    /* the root iblock is protected, and we have no
+                     * legitimate way of getting a pointer to it.
+                     *
+                     * We square this circle by using the 
+                     * H5AC_get_entry_ptr_from_addr() to get the needed
+                     * pointer.
+                     *
+                     * WARNING: This call should be used only in debugging
+                     *          routines, and it should be avoided there when
+                     *          possible.
+                     *
+                     *          Further, if we ever multi-thread the cache,
+                     *          this routine will have to be either discarded
+                     *          or heavily re-worked.
+                     *
+                     *          Finally, keep in mind that the entry whose
+                     *          pointer is obtained in this fashion may not
+                     *          be in a stable state.
+                     *
+                     * Assuming that the flush dependency code is working
+                     * as it should, the only reason for the root iblock to
+                     * be unpinned is if none of its children are in cache.
+                     * This unfortunately means that if it is protected and
+                     * not pinned, the fractal heap is in the process of loading
+                     * or inserting one of its children.  The obvious 
+                     * implication is that there is a significant chance that 
+                     * the root iblock is in an unstable state.
+                     *
+                     * All this suggests that using 
+                     * H5AC_get_entry_ptr_from_addr() to obtain the pointer 
+                     * to the protected root iblock is questionable here.  
+                     * However, since this is test/debugging code, I expect 
+                     * that we will use this approach until it causes problems,
+                     *  or we think of a better way.
+                     */
+                    if(H5AC_get_entry_ptr_from_addr(f, root_iblock_addr, (void **)(&root_iblock)) < 0)
+                        HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "H5AC_get_entry_ptr_from_addr() failed.")
+                    HDassert(root_iblock);
+                } /* end else */
+            } /* end if */
+            else {      /* root_iblock != NULL */
+                /* we have the pointer to the root iblock.  Protect it 
+                 * if it is neither pinned nor protected -- otherwise we 
+                 * are ready to go.
+                 */
+                 H5HF_indirect_t *   iblock = NULL;
+
+                 if(((root_iblock_status & H5AC_ES__IS_PINNED) == 0) &&
+                     ((root_iblock_status & H5AC_ES__IS_PROTECTED) == 0)) {
+                    /* the root iblock is neither pinned nor protected -- hence
+                     * we must protect it before we proceed
+                     *
+                     * Note that the udata is only used in the load callback.
+                     * While the fractal heap makes heavy use of the udata
+                     * in this case, since we know that the entry is in cache,
+                     * we can pass NULL udata.
+                     *
+                     * The tag associated specified in the dxpl we received
+                     * as a parameter (via dxpl_id) may not be correct.
+                     * Grab the (hopefully) correct tag from the header,
+                     * and load it into the dxpl via the H5_BEGIN_TAG and 
+                     * H5_END_TAG macros.  Note that any error bracked by
+                     * these macros must be reported with HGOTO_ERROR_TAG. 
+                     */
+                    H5_BEGIN_TAG(dxpl_id, hdr->heap_addr, FAIL)
+
+                    if(NULL == (iblock = (H5HF_indirect_t *)H5AC_protect(f, dxpl_id, H5AC_FHEAP_IBLOCK, root_iblock_addr, NULL, H5AC__READ_ONLY_FLAG)))
+                        HGOTO_ERROR_TAG(H5E_HEAP, H5E_CANTPROTECT, FAIL, "H5AC_protect() faild.")
+
+                    H5_END_TAG(FAIL)
+
+                    unprotect_root_iblock = TRUE;
+                    HDassert(iblock == root_iblock);
+                } /* end if */
+            } /* end else */
+
+            /* at this point, one way or another, the root iblock is locked
+             * in memory for the duration of the call.  Do some sanity checks,
+             * and then call H5HF__cache_verify_iblock_descendants_clean().
+             */
+             HDassert(root_iblock->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
+             HDassert(root_iblock->cache_info.type == H5AC_FHEAP_IBLOCK);
+
+             if(H5HF__cache_verify_iblock_descendants_clean(f, dxpl_id, hdr->heap_addr, root_iblock, &root_iblock_status, fd_clean, clean) < 0)
+                 HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "can't verify root iblock & descendants clean.")
+
+             /* Unprotect the root indirect block if required */
+             if(unprotect_root_iblock) {
+                HDassert(root_iblock);
+                if(H5AC_unprotect(f, dxpl_id, H5AC_FHEAP_IBLOCK, root_iblock_addr, root_iblock, H5AC__NO_FLAGS_SET) < 0)
+                    HGOTO_ERROR(H5E_HEAP, H5E_CANTUNPROTECT, FAIL, "H5AC_unprotect() faild.")
+            } /* end if */
+        } /* end else */
     } /* end if */
     else if((hdr->man_dtable.curr_root_rows == 0) &&
 		(HADDR_UNDEF != hdr->man_dtable.table_addr)) {
         haddr_t		root_dblock_addr;
         unsigned	root_dblock_status = 0;
+        hbool_t         in_cache;
+        hbool_t         type_ok;
 
 	/* this is scenario 2 -- we have a root dblock */
 	root_dblock_addr = hdr->man_dtable.table_addr;
@@ -2688,25 +2907,48 @@ H5HF__cache_verify_hdr_descendants_clean(H5F_t *f, H5HF_hdr_t *hdr,
             HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't get root dblock status")
 
 	if(root_dblock_status & H5AC_ES__IN_CACHE) {
+            if(H5AC_verify_entry_type(f, root_dblock_addr, &H5AC_FHEAP_DBLOCK[0], &in_cache, &type_ok) < 0)
+                HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check dblock type")
+            HDassert(in_cache);
+            if(!type_ok)
+                HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "root dblock addr doesn't refer to a dblock?!?")
+
             /* If a root dblock is in cache, it must have a flush
-             * dependency relationship with the header.
+             * dependency relationship with the header, and it
+             * may not be the parent in any flush dependency
+             * relationship.
+             *
+             * We don't test this fully, but we will verify that
+             * the root iblock is a child in a flush dependency
+             * relationship with the header.
              */
-            if(0 == (root_dblock_status & H5AC_ES__IS_FLUSH_DEP_CHILD))
-                HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "root dblock in cache and not a flush dep child.")
+            if(H5AC_flush_dependency_exists(f, hdr->heap_addr, root_dblock_addr, &fd_exists) < 0)
+                HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check flush dependency")
+            if(!fd_exists)
+                HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "root dblock is not a flush dep parent of header.")
+
             if(0 != (root_dblock_status & H5AC_ES__IS_FLUSH_DEP_PARENT))
                 HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "root dblock in cache and is a flush dep parent.")
 
-	    if(root_dblock_status & H5AC_ES__IS_DIRTY)
-                *clean = FALSE;
-	} /* end if */
-        else    /* root dblock not in cache */
-	    *clean = TRUE;
+            *clean = !((root_dblock_status & H5AC_ES__IS_DIRTY) &&
+                       (((root_dblock_status & 
+                          H5AC_ES__IMAGE_IS_UP_TO_DATE) == 0) || 
+                        (!H5AC_get_serialization_in_progress(f))));
+
+            *fd_clean = *clean;
+        } /* end if */
+        else {    /* root dblock not in cache */
+            *fd_clean = TRUE;
+            *clean = TRUE;
+        } /* end else */
     } /* end else-if */
-    else
-	/* this is scenario 3 -- the fractal heap is empty, and we 
-	 * have nothing to do. 
-	 */
-	*clean = TRUE;
+    else {
+        /* this is scenario 3 -- the fractal heap is empty, and we 
+         * have nothing to do. 
+         */
+        *fd_clean = TRUE;
+        *clean = TRUE;
+    } /* end else */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -2741,6 +2983,40 @@ done:
  *		H5HF__cache_verify_descendant_iblocks_clean() are 
  *		recursive co-routines.
  *
+ *		Update -- 9/29/16
+ *
+ *		The implementation of flush dependencies has been changed.
+ *		Prior to this change, a flush dependency parent could be 
+ *		flushed if and only if all its flush dependency decendants
+ *		were clean.  In the new definition, a flush dependency 
+ *		parent can be flushed if all its immediate flush dependency
+ *		children are clean, regardless of any other dirty 
+ *		decendants.  
+ *
+ *		Further, metadata cache entries are now allowed to have 
+ *		multiple flush dependency parents.  
+ *
+ *		This means that the fractal heap is no longer ncessarily 
+ *		flushed from the bottom up.
+ *
+ *		For example, it is now possible for a dirty fractal heap 
+ *		header to be flushed before a dirty dblock, as long as the
+ *		there in an interviening iblock, and the header has no 
+ *		dirty immediate flush dependency children.
+ *
+ *		Also, I gather that under some circumstances, a dblock 
+ *		will be direct a flush dependency child both of the iblock 
+ *		that points to it, and of the fractal heap header.
+ *
+ *		As a result of these changes, the functionality of these
+ *		sanity checking routines has been modified significantly.
+ *		Instead of scanning the fractal heap from a starting point
+ *		down, and verifying that there were no dirty entries, the 
+ *		functions now scan downward from the starting point and 
+ *		verify that there are no dirty flush dependency children 
+ *		of the specified flush dependency parent.  In passing, 
+ *		they also walk the data structure, and verify it.
+ *
  * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:	John Mainzer
@@ -2750,8 +3026,9 @@ done:
  */
 #ifndef NDEBUG
 static herr_t
-H5HF__cache_verify_iblock_descendants_clean(H5F_t *f, H5HF_indirect_t *iblock,
-    unsigned *iblock_status, hbool_t *clean)
+H5HF__cache_verify_iblock_descendants_clean(H5F_t *f, hid_t dxpl_id,
+    haddr_t fd_parent_addr, H5HF_indirect_t *iblock, unsigned *iblock_status, 
+    hbool_t * fd_clean, hbool_t *clean)
 {
     hbool_t	has_dblocks = FALSE;
     hbool_t	has_iblocks = FALSE;
@@ -2761,17 +3038,19 @@ H5HF__cache_verify_iblock_descendants_clean(H5F_t *f, H5HF_indirect_t *iblock,
 
     /* Sanity checks */
     HDassert(f);
+    HDassert(H5F_addr_defined(fd_parent_addr));
     HDassert(iblock);
     HDassert(iblock->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
     HDassert(iblock->cache_info.type == H5AC_FHEAP_IBLOCK);
     HDassert(iblock_status);
-    HDassert(clean);
-    HDassert(*clean);
+    HDassert(fd_clean);
+    HDassert(*fd_clean);
+    HDassert(clean); /* note that *clean need not be TRUE */
 
-    if((*clean) && H5HF__cache_verify_iblocks_dblocks_clean(f, iblock, clean, &has_dblocks) < 0)
+    if((*fd_clean) && H5HF__cache_verify_iblocks_dblocks_clean(f, fd_parent_addr, iblock, fd_clean, clean, &has_dblocks) < 0)
         HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "can't verify dblocks clean.")
 
-    if((*clean) && H5HF__cache_verify_descendant_iblocks_clean(f, iblock, clean, &has_iblocks) < 0)
+    if((*fd_clean) && H5HF__cache_verify_descendant_iblocks_clean(f, dxpl_id, fd_parent_addr, iblock, fd_clean, clean, &has_iblocks) < 0)
         HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "can't verify iblocks clean.")
 
     /* verify that flush dependency setup is plausible */
@@ -2808,6 +3087,53 @@ done:
  *		during the call.  Caller must ensure that this is 
  *		the case before the call.
  *
+ *      Update -- 8/24/15
+ *
+ *      With the advent of the metadata cache image feature, it is
+ *      possible for the pre-serialize and serialize calls to be
+ *      invoked outside of a flush.  While this serialization
+ *      observes flush dependencies for the order of serialization,
+ *      the entries are not written to disk, and hence dirty entries
+ *      remain dirty.
+ *
+ *      To address this, updated the sanity checks in this function
+ *      to treat entries whose images are up to date as clean if
+ *      a cache serialization is in progress.
+ *
+ *		Update -- 9/29/16
+ *
+ *		The implementation of flush dependencies has been changed.
+ *		Prior to this change, a flush dependency parent could be 
+ *		flushed if and only if all its flush dependency decendants
+ *		were clean.  In the new definition, a flush dependency 
+ *		parent can be flushed if all its immediate flush dependency
+ *		children are clean, regardless of any other dirty 
+ *		decendants.  
+ *
+ *		Further, metadata cache entries are now allowed to have 
+ *		multiple flush dependency parents.  
+ *
+ *		This means that the fractal heap is no longer ncessarily 
+ *		flushed from the bottom up.
+ *
+ *		For example, it is now possible for a dirty fractal heap 
+ *		header to be flushed before a dirty dblock, as long as the
+ *		there in an interviening iblock, and the header has no 
+ *		dirty immediate flush dependency children.
+ *
+ *		Also, I gather that under some circumstances, a dblock 
+ *		will be direct a flush dependency child both of the iblock 
+ *		that points to it, and of the fractal heap header.
+ *
+ *		As a result of these changes, the functionality of these
+ *		sanity checking routines has been modified significantly.
+ *		Instead of scanning the fractal heap from a starting point
+ *		down, and verifying that there were no dirty entries, the 
+ *		functions now scan downward from the starting point and 
+ *		verify that there are no dirty flush dependency children 
+ *		of the specified flush dependency parent.  In passing, 
+ *		they also walk the data structure, and verify it.
+ *
  * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:	John Mainzer
@@ -2817,53 +3143,82 @@ done:
  */
 #ifndef NDEBUG
 static herr_t
-H5HF__cache_verify_iblocks_dblocks_clean(H5F_t *f, H5HF_indirect_t *iblock, 
-    hbool_t *clean, hbool_t *has_dblocks)
+H5HF__cache_verify_iblocks_dblocks_clean(H5F_t *f, haddr_t fd_parent_addr, 
+    H5HF_indirect_t *iblock, hbool_t *fd_clean, hbool_t *clean, 
+    hbool_t *has_dblocks)
 {
     unsigned	num_direct_rows;
     unsigned	max_dblock_index;
     unsigned    i;
+    haddr_t	iblock_addr;
     herr_t      ret_value = SUCCEED;      /* Return value */
 
     FUNC_ENTER_STATIC
 
     /* Sanity checks */
     HDassert(f);
+    HDassert(H5F_addr_defined(fd_parent_addr));
     HDassert(iblock);
     HDassert(iblock->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
     HDassert(iblock->cache_info.type == H5AC_FHEAP_IBLOCK);
-    HDassert(clean);
-    HDassert(*clean);
+    HDassert(fd_clean);
+    HDassert(*fd_clean);
+    HDassert(clean); /* note that *clean need not be true */
     HDassert(has_dblocks);
 
     i = 0;
     num_direct_rows = MIN(iblock->nrows, iblock->hdr->man_dtable.max_direct_rows);
     HDassert(num_direct_rows <= iblock->nrows);
     max_dblock_index = (num_direct_rows * iblock->hdr->man_dtable.cparam.width) - 1;
-    while((*clean) && (i <= max_dblock_index)) {
+    iblock_addr = iblock->addr;
+    HDassert(H5F_addr_defined(iblock_addr));
+
+    while((*fd_clean) && (i <= max_dblock_index)) {
         haddr_t     dblock_addr;
 
         dblock_addr = iblock->ents[i].addr;
 	if(H5F_addr_defined(dblock_addr)) {
-            unsigned 	dblock_status = 0;
+            hbool_t	in_cache;
+            hbool_t	type_ok;
+
+            if(H5AC_verify_entry_type(f, dblock_addr, &H5AC_FHEAP_DBLOCK[0], &in_cache, &type_ok) < 0)
+                HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check dblock type")
+
+            if(in_cache) { /* dblock is in cache */
+                hbool_t 	fd_exists;
+                unsigned 	dblock_status = 0;
+
+                if(!type_ok)
+                    HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "dblock addr doesn't refer to a dblock?!?")
+
+                if(H5AC_get_entry_status(f, dblock_addr, &dblock_status) < 0)
+                    HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't get dblock status")
+
+                HDassert(dblock_status & H5AC_ES__IN_CACHE);
 
-            if(H5AC_get_entry_status(f, dblock_addr, &dblock_status) < 0)
-                HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't get dblock status")
-            if(dblock_status & H5AC_ES__IN_CACHE) {
                 *has_dblocks = TRUE;
 
-                if(dblock_status & H5AC_ES__IS_DIRTY)
+                if((dblock_status & H5AC_ES__IS_DIRTY) &&
+                        (((dblock_status & H5AC_ES__IMAGE_IS_UP_TO_DATE) == 0) ||
+                        (!H5AC_get_serialization_in_progress(f)))) {
                     *clean = FALSE;
+		    
+                    if(H5AC_flush_dependency_exists(f, fd_parent_addr, dblock_addr, &fd_exists) < 0)
+                        HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check flush dependency")
+
+                    if(fd_exists) 
+                        *fd_clean = FALSE;
+                } /* end if */
 
-	        /* If a child dblock is in cache, it must have a flush 
-                 * dependency relationship with this iblock, and it 
-                 * may not be the parent in any flush dependency 
-                 * relationship.  
+                /* If a child dblock is in cache, it must have a flush 
+                 * dependency relationship with this iblock.  Test this 
+                 * here.
                  */
-	        if(0 == (dblock_status & H5AC_ES__IS_FLUSH_DEP_CHILD))
-		    HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "dblock in cache and not a flush dep child.")
-                if(0 != (dblock_status & H5AC_ES__IS_FLUSH_DEP_PARENT)) 
-		    HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "dblock in cache and is a flush dep parent.")
+                 if(H5AC_flush_dependency_exists(f, iblock_addr, dblock_addr, &fd_exists) < 0)
+                    HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check flush dependency")
+
+                if(!fd_exists)
+                    HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "dblock in cache and not a flush dep child of iblock.")
             } /* end if */
         } /* end if */
 
@@ -2896,6 +3251,54 @@ done:
  *		during the call.  Caller must ensure that this is 
  *		the case before the call.
  *
+ *              Update -- 8/24/15
+ *
+ *              With the advent of the metadata cache image feature, it is
+ *              possible for the pre-serialize and serialize calls to be
+ *              invoked outside of a flush.  While this serialization
+ *              observes flush dependencies for the order of serialization,
+ *              the entries are not written to disk, and hence dirty entries
+ *              remain dirty.
+ *
+ *              To address this, updated the sanity checks in this function
+ *              to treat entries whose images are up to date as clean if
+ *              a cache serialization is in progress.
+ *
+ *		Update -- 9/29/16
+ *
+ *		The implementation of flush dependencies has been changed.
+ *		Prior to this change, a flush dependency parent could be 
+ *		flushed if and only if all its flush dependency decendants
+ *		were clean.  In the new definition, a flush dependency 
+ *		parent can be flushed if all its immediate flush dependency
+ *		children are clean, regardless of any other dirty 
+ *		decendants.  
+ *
+ *		Further, metadata cache entries are now allowed to have 
+ *		multiple flush dependency parents.
+ *
+ *		This means that the fractal heap is no longer ncessarily 
+ *		flushed from the bottom up.
+ *
+ *		For example, it is now possible for a dirty fractal heap 
+ *		header to be flushed before a dirty dblock, as long as the
+ *		there in an interviening iblock, and the header has no 
+ *		dirty immediate flush dependency children.
+ *
+ *		Also, I gather that under some circumstances, a dblock 
+ *		will be direct a flush dependency child both of the iblock 
+ *		that points to it, and of the fractal heap header.
+ *
+ *		As a result of these changes, the functionality of these
+ *		sanity checking routines has been modified significantly.
+ *		Instead of scanning the fractal heap from a starting point
+ *		down, and verifying that there were no dirty entries, the 
+ *		functions now scan downward from the starting point and 
+ *		verify that there are no dirty flush dependency children 
+ *		of the specified flush dependency parent.  In passing, 
+ *		they also walk the data structure, and verify it.
+ *
+ *
  * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:	John Mainzer
@@ -2905,33 +3308,38 @@ done:
  */
 #ifndef NDEBUG
 static herr_t
-H5HF__cache_verify_descendant_iblocks_clean(H5F_t *f, H5HF_indirect_t *iblock,
+H5HF__cache_verify_descendant_iblocks_clean(H5F_t *f, hid_t dxpl_id,
+    haddr_t fd_parent_addr, H5HF_indirect_t *iblock, hbool_t *fd_clean,
     hbool_t *clean, hbool_t *has_iblocks)
 {
     unsigned	      first_iblock_index;
     unsigned	      last_iblock_index;
     unsigned	      num_direct_rows;
     unsigned	      i;
+    haddr_t    	      iblock_addr;
     herr_t            ret_value = SUCCEED;      /* Return value */
 
     FUNC_ENTER_STATIC
 
     /* Sanity checks */
     HDassert(f);
+    HDassert(H5F_addr_defined(fd_parent_addr));
     HDassert(iblock);
     HDassert(iblock->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
     HDassert(iblock->cache_info.type == H5AC_FHEAP_IBLOCK);
-    HDassert(clean);
-    HDassert(*clean);
+    HDassert(fd_clean);
+    HDassert(*fd_clean);
+    HDassert(clean); /* note that *clean need not be true */
     HDassert(has_iblocks);
     num_direct_rows = MIN(iblock->nrows, iblock->hdr->man_dtable.max_direct_rows);
     HDassert(num_direct_rows <= iblock->nrows);
 
+    iblock_addr = iblock->addr;
     first_iblock_index = num_direct_rows * iblock->hdr->man_dtable.cparam.width;
     last_iblock_index = (iblock->nrows * iblock->hdr->man_dtable.cparam.width) - 1;
 
     i = first_iblock_index;
-    while((*clean) && (i <= last_iblock_index)) {
+    while((*fd_clean) && (i <= last_iblock_index)) {
         haddr_t           child_iblock_addr = iblock->ents[i].addr;
 
 	if(H5F_addr_defined(child_iblock_addr)) {
@@ -2941,9 +3349,157 @@ H5HF__cache_verify_descendant_iblocks_clean(H5F_t *f, H5HF_indirect_t *iblock,
                 HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't get iblock status")
 
 	    if(child_iblock_status & H5AC_ES__IN_CACHE) {
+                hbool_t         fd_exists;
+
 	        *has_iblocks = TRUE;
-                if(child_iblock_status & H5AC_ES__IS_DIRTY)
-		    *clean = FALSE;
+
+                if((child_iblock_status & H5AC_ES__IS_DIRTY) &&
+                        (((child_iblock_status & H5AC_ES__IMAGE_IS_UP_TO_DATE) == 0) ||
+                        (!H5AC_get_serialization_in_progress(f)))) {
+
+                    *clean = FALSE;
+
+                    if(H5AC_flush_dependency_exists(f, fd_parent_addr, child_iblock_addr, &fd_exists) < 0)
+                        HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check flush dependency")
+
+                    if(fd_exists)
+                        *fd_clean = FALSE;
+                } /* end if */
+
+                /* if the child iblock is in cache and *fd_clean is TRUE, 
+                 * we must continue to explore down the fractal heap tree
+                 * structure to verify that all descendant blocks that are 
+                 * flush dependency children of the entry at parent_addr are 
+                 * either clean, or not in the metadata cache.  We do this 
+                 * with a recursive call to 
+                 * H5HF__cache_verify_iblock_descendants_clean().
+                 * However, we can't make this call unless the child iblock
+                 * is somehow locked into the cache -- typically via either 
+                 * pinning or protecting.
+                 *
+                 * If the child iblock is pinned, we can look up its pointer
+                 * on the current iblock's pinned child iblock list, and 
+                 * and use that pointer in the recursive call.
+                 *
+                 * If the entry is unprotected and unpinned, we simply
+                 * protect it.
+                 *
+                 * If, however, the the child iblock is already protected, 
+                 * but not pinned, we have a bit of a problem, as we have 
+                 * no legitimate way of looking up its pointer in memory.
+                 *
+                 * To solve this problem, I have added a new metadata cache
+                 * call to obtain the pointer.  
+                 *
+                 * WARNING: This call should be used only in debugging 
+                 * 	    routines, and it should be avoided there when 
+                 *	    possible.  
+                 *
+                 *          Further, if we ever multi-thread the cache, 
+                 *	    this routine will have to be either discarded 
+                 *	    or heavily re-worked.
+                 *
+                 *	    Finally, keep in mind that the entry whose 
+                 *	    pointer is obtained in this fashion may not 
+                 *          be in a stable state.  
+                 *
+                 * Assuming that the flush dependency code is working 
+                 * as it should, the only reason for the child entry to 
+                 * be unpinned is if none of its children are in cache.
+                 * This unfortunately means that if it is protected and 
+                 * not pinned, the fractal heap is in the process of loading
+                 * or inserting one of its children.  The obvious implication
+                 * is that there is a significant chance that the child 
+                 * iblock is in an unstable state.
+                 *
+                 * All this suggests that using the new call to obtain the 
+                 * pointer to the protected child iblock is questionable 
+                 * here.  However, since this is test/debugging code, I
+                 * expect that we will use this approach until it causes
+                 * problems, or we think of a better way.
+                 */
+                if(*fd_clean) {
+                    H5HF_indirect_t *child_iblock = NULL;
+                    hbool_t unprotect_child_iblock = FALSE;
+
+                    if(0 == (child_iblock_status & H5AC_ES__IS_PINNED)) {
+                        /* child iblock is not pinned */
+                        if(0 == (child_iblock_status & H5AC_ES__IS_PROTECTED)) {
+                            /* child iblock is unprotected, and unpinned */
+                            /* protect it.  Note that the udata is only  */
+                            /* used in the load callback.  While the     */
+                            /* fractal heap makes heavy use of the udata */
+                            /* in this case, since we know that the      */
+                            /* entry is in cache, we can pass NULL udata */
+                            /*                                           */
+                            /* The tag associated specified in the dxpl  */
+                            /* we received as a parameter (via dxpl_id)  */
+                            /* may not be correct.                       */
+                            /*                                           */
+                            /* Grab the (hopefully) correct tag from the */
+                            /* parent iblock, and load it into the dxpl  */
+                            /* via the H5_BEGIN_TAG and H5_END_TAG       */
+                            /* macros.  Note that any error bracked by   */
+                            /* these macros must be reported with        */
+                            /* HGOTO_ERROR_TAG.                          */
+
+                            H5_BEGIN_TAG(dxpl_id, iblock->hdr->heap_addr, FAIL)
+
+                            if(NULL == (child_iblock = (H5HF_indirect_t *) H5AC_protect(f, dxpl_id, H5AC_FHEAP_IBLOCK, child_iblock_addr, NULL, H5AC__READ_ONLY_FLAG)))
+                                HGOTO_ERROR_TAG(H5E_HEAP, H5E_CANTPROTECT, FAIL, "H5AC_protect() faild.")
+
+                            H5_END_TAG(FAIL)
+
+                            unprotect_child_iblock = TRUE;
+                        } /* end if */
+                        else {
+                            /* child iblock is protected -- use             */
+                            /* H5AC_get_entry_ptr_from_addr() to get a      */
+                            /* pointer to the entry.  This is very slimy -- */
+                            /* come up with a better solution.              */
+                            if(H5AC_get_entry_ptr_from_addr(f, child_iblock_addr, (void **)(&child_iblock)) < 0)
+                                HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "H5AC_get_entry_ptr_from_addr() faild.")
+                            HDassert(child_iblock);
+                        } /* end else */
+                    } /* end if */
+                    else {
+                        /* child iblock is pinned -- look it up in the */
+                        /* parent iblocks child_iblocks array.         */
+                        HDassert(iblock->child_iblocks);
+                        child_iblock = iblock->child_iblocks[i - first_iblock_index];
+                    } /* end else */
+
+                    /* At this point, one way or another we should have 
+                     * a pointer to the child iblock.  Verify that we 
+                     * that we have the correct one.
+                     */
+                    HDassert(child_iblock);
+                    HDassert(child_iblock->cache_info.magic == H5C__H5C_CACHE_ENTRY_T_MAGIC);
+                    HDassert(child_iblock->cache_info.type == H5AC_FHEAP_IBLOCK);
+                    HDassert(child_iblock->addr == child_iblock_addr);
+
+                    /* now make the recursive call */
+                    if(H5HF__cache_verify_iblock_descendants_clean(f, dxpl_id, fd_parent_addr, child_iblock, &child_iblock_status, fd_clean, clean) < 0)
+                        HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "can't verify child iblock clean.")
+
+                    /* if iblock_addr != fd_parent_addr, verify that a flush 
+                     * dependency relationship exists between iblock and 
+                     * the child iblock.
+                     */
+                    if(fd_parent_addr != iblock_addr) {
+                        if(H5AC_flush_dependency_exists(f, iblock_addr, child_iblock_addr, &fd_exists) < 0)
+                            HGOTO_ERROR(H5E_HEAP, H5E_CANTGET, FAIL, "can't check flush dependency")
+
+                        if(!fd_exists)
+                            HGOTO_ERROR(H5E_HEAP, H5E_SYSTEM, FAIL, "iblock is not a flush dep parent of child_iblock.")
+                    } /* end if */
+
+                    /* if we protected the child iblock, unprotect it now */
+                    if(unprotect_child_iblock) {
+                        if(H5AC_unprotect(f, dxpl_id, H5AC_FHEAP_IBLOCK, child_iblock_addr, child_iblock, H5AC__NO_FLAGS_SET) < 0)
+                            HGOTO_ERROR(H5E_HEAP, H5E_CANTUNPROTECT, FAIL, "H5AC_unprotect() faild.")
+                    } /* end if */
+                } /* end if */
             } /* end if */
         } /* end if */
 
diff --git a/src/H5MF.c b/src/H5MF.c
index 3ed6d28..3a6a953 100644
--- a/src/H5MF.c
+++ b/src/H5MF.c
@@ -1489,7 +1489,7 @@ H5MF_settle_raw_data_fsm(H5F_t *f, hid_t dxpl_id, hbool_t *fsm_settled)
             fsinfo.fs_addr[type-1] = HADDR_UNDEF;
         fsinfo.strategy = f->shared->fs_strategy;
         fsinfo.threshold = f->shared->fs_threshold;
-        if(H5F_super_ext_write_msg(f, dxpl_id, H5O_FSINFO_ID, &fsinfo, TRUE) < 0)
+        if(H5F_super_ext_write_msg(f, dxpl_id, H5O_FSINFO_ID, &fsinfo, TRUE, H5O_MSG_NO_FLAGS_SET) < 0)
             HGOTO_ERROR(H5E_FSPACE, H5E_WRITEERROR, FAIL, "error in writing message to superblock extension")
 
 
@@ -2113,7 +2113,7 @@ HDfprintf(stderr, "%s: Entering\n", FUNC);
 	fsinfo.threshold = f->shared->fs_threshold;
 
         /* Write the free space manager message -- message must already exist */
-        if(H5F_super_ext_write_msg(f, dxpl_id, H5O_FSINFO_ID, &fsinfo, FALSE) < 0)
+        if(H5F_super_ext_write_msg(f, dxpl_id, H5O_FSINFO_ID, &fsinfo, FALSE, H5O_MSG_NO_FLAGS_SET) < 0)
             HGOTO_ERROR(H5E_RESOURCE, H5E_WRITEERROR, FAIL, "error in writing message to superblock extension")
 
 	/* Final close of free-space managers */
diff --git a/src/H5O.c b/src/H5O.c
index e0c0f0b..1b58703 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -130,11 +130,12 @@ const H5O_msg_class_t *const H5O_msg_class_g[] = {
     H5O_MSG_AINFO,		/*0x0015 Attribute information		*/
     H5O_MSG_REFCOUNT,		/*0x0016 Object's ref. count		*/
     H5O_MSG_FSINFO,		/*0x0017 Free-space manager info        */
-    H5O_MSG_UNKNOWN,		/*0x0018 Placeholder for unknown message */
+    H5O_MSG_MDCI,               /*0x0018 Metadata cache image           */
+    H5O_MSG_UNKNOWN,		/*0x0019 Placeholder for unknown message */
 #ifdef H5O_ENABLE_BOGUS
-    H5O_MSG_BOGUS_INVALID, 	/*0x0019 "Bogus invalid" (for testing) 	*/
+    H5O_MSG_BOGUS_INVALID, 	/*0x001A "Bogus invalid" (for testing) 	*/
 #else /* H5O_ENABLE_BOGUS */
-    NULL,                       /*0x0019 "Bogus invalid" (for testing) 	*/
+    NULL,                       /*0x001A "Bogus invalid" (for testing) 	*/
 #endif /* H5O_ENABLE_BOGUS */
 };
 
diff --git a/src/H5Opkg.h b/src/H5Opkg.h
index c2866f7..e1fa0be 100644
--- a/src/H5Opkg.h
+++ b/src/H5Opkg.h
@@ -31,7 +31,7 @@
 #define H5O_NMESGS	8 		/*initial number of messages	     */
 #define H5O_NCHUNKS	2		/*initial number of chunks	     */
 #define H5O_MIN_SIZE	22		/* Min. obj header data size (must be big enough for a message prefix and a continuation message) */
-#define H5O_MSG_TYPES   26              /* # of types of messages            */
+#define H5O_MSG_TYPES   27              /* # of types of messages            */
 #define H5O_MAX_CRT_ORDER_IDX 65535     /* Max. creation order index value   */
 
 /* Versions of object header structure */
@@ -538,7 +538,10 @@ H5_DLLVAR const H5O_msg_class_t H5O_MSG_REFCOUNT[1];
 /* Free-space Manager Info message. (0x0017) */
 H5_DLLVAR const H5O_msg_class_t H5O_MSG_FSINFO[1];
 
-/* Placeholder for unknown message. (0x0018) */
+/* Metadata Cache Image message. (0x0018) */
+H5_DLLVAR const H5O_msg_class_t H5O_MSG_MDCI[1];
+
+/* Placeholder for unknown message. (0x0019) */
 H5_DLLVAR const H5O_msg_class_t H5O_MSG_UNKNOWN[1];
 
 
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index f6df874..71c512c 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -69,6 +69,7 @@ typedef struct H5O_t H5O_t;
 #define H5O_FIRST	(-2)		/* Operate on first message of type  */
 
 /* Flags needed when encoding messages */
+#define H5O_MSG_NO_FLAGS_SET	0x00u
 #define H5O_MSG_FLAG_CONSTANT	0x01u
 #define H5O_MSG_FLAG_SHARED	0x02u
 #define H5O_MSG_FLAG_DONTSHARE	0x04u
@@ -204,7 +205,8 @@ typedef struct H5O_copy_t {
 #define H5O_AINFO_ID    0x0015          /* Attribute info message.  */
 #define H5O_REFCOUNT_ID 0x0016          /* Reference count message.  */
 #define H5O_FSINFO_ID   0x0017          /* File space info message.  */
-#define H5O_UNKNOWN_ID  0x0018          /* Placeholder message ID for unknown message.  */
+#define H5O_MDCI_MSG_ID 0x0018		/* Metadata Cache Image Message */
+#define H5O_UNKNOWN_ID  0x0019          /* Placeholder message ID for unknown message.  */
                                         /* (this should never exist in a file) */
 /* 
  * Note: Must increment H5O_MSG_TYPES in H5Opkg.h and update H5O_msg_class_g
@@ -214,7 +216,7 @@ typedef struct H5O_copy_t {
  *
  * (this should never exist in a file)
  */
-#define H5O_BOGUS_INVALID_ID	0x0019  /* "Bogus invalid" Message.  */
+#define H5O_BOGUS_INVALID_ID	0x001A  /* "Bogus invalid" Message.  */
 
 /* Shared object message types.
  * Shared objects can be committed, in which case the shared message contains
@@ -794,6 +796,16 @@ typedef struct H5O_fsinfo_t {
     haddr_t     	  fs_addr[H5FD_MEM_NTYPES-1]; /* Addresses of free space managers */
 } H5O_fsinfo_t;
 
+/*
+ * Metadata Cache Image Message.
+ * Contains base address and length of the metadata cache image.
+ * (Data structure in memory)
+ */
+typedef struct H5O_mdci_t {
+    haddr_t	addr;			/* address of MDC image block */
+    hsize_t	size;			/* size of MDC image block    */
+} H5O_mdci_t;
+
 /* Typedef for "application" iteration operations */
 typedef herr_t (*H5O_operator_t)(const void *mesg/*in*/, unsigned idx,
     void *operator_data/*in,out*/);
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index 91a0e03..7ea0fe0 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -225,6 +225,13 @@
 #define H5F_ACS_COLL_MD_WRITE_FLAG_ENC    H5P__encode_hbool_t
 #define H5F_ACS_COLL_MD_WRITE_FLAG_DEC    H5P__decode_hbool_t
 #endif /* H5_HAVE_PARALLEL */
+/* Definitions for the initial metadata cache image configuration */
+#define H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_SIZE sizeof(H5AC_cache_image_config_t)
+#define H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_DEF  H5AC__DEFAULT_CACHE_IMAGE_CONFIG
+#define H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_ENC  H5P__facc_cache_image_config_enc
+#define H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_DEC  H5P__facc_cache_image_config_dec
+#define H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_CMP  H5P__facc_cache_image_config_cmp
+
 
 /******************/
 /* Local Typedefs */
@@ -279,6 +286,11 @@ static herr_t H5P_facc_mdc_log_location_copy(const char *name, size_t size, void
 static int    H5P_facc_mdc_log_location_cmp(const void *value1, const void *value2, size_t size);
 static herr_t H5P_facc_mdc_log_location_close(const char *name, size_t size, void *value);
 
+/* Metadata cache image property callbacks */
+static int H5P__facc_cache_image_config_cmp(const void *_config1, const void *_config2, size_t H5_ATTR_UNUSED size);
+static herr_t H5P__facc_cache_image_config_enc(const void *value, void **_pp, size_t *size);
+static herr_t H5P__facc_cache_image_config_dec(const void **_pp, void *_value);
+
 
 /*********************/
 /* Package Variables */
@@ -346,6 +358,7 @@ static const hbool_t H5F_def_evict_on_close_flag_g = H5F_ACS_EVICT_ON_CLOSE_FLAG
 static const H5P_coll_md_read_flag_t H5F_def_coll_md_read_flag_g = H5F_ACS_COLL_MD_READ_FLAG_DEF;  /* Default setting for the collective metedata read flag */
 static const hbool_t H5F_def_coll_md_write_flag_g = H5F_ACS_COLL_MD_WRITE_FLAG_DEF;  /* Default setting for the collective metedata write flag */
 #endif /* H5_HAVE_PARALLEL */
+static const H5AC_cache_image_config_t H5F_def_mdc_initCacheImageCfg_g = H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_DEF;  /* Default metadata cache image settings */
 
 
 /*-------------------------------------------------------------------------
@@ -555,6 +568,12 @@ H5P__facc_reg_prop(H5P_genclass_t *pclass)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
 #endif /* H5_HAVE_PARALLEL */
 
+    /* Register the initial metadata cache image configuration */
+    if(H5P_register_real(pclass, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_NAME, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_SIZE, &H5F_def_mdc_initCacheImageCfg_g, 
+            NULL, NULL, NULL, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_ENC, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_DEC, 
+            NULL, NULL, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_CMP, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5P__facc_reg_prop() */
@@ -1543,6 +1562,101 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5Pset_mdc_image_config
+ *
+ * Purpose:	Set the initial metadata cache image configuration in the
+ *		target FAPL.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	J. Mainzer
+ *              Thursday, June 25, 2015
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_mdc_image_config(hid_t plist_id, H5AC_cache_image_config_t *config_ptr)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", plist_id, config_ptr);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id,H5P_FILE_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* validate the new configuration */
+    if(H5AC_validate_cache_image_config(config_ptr) < 0)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid metadata cache image configuration")
+
+    /* set the modified metadata cache image config */
+
+    /* If we ever support multiple versions of H5AC_cache_image_config_t, we
+     * will have to test the version and do translation here.
+     */
+
+    if(H5P_set(plist, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_NAME, config_ptr) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set metadata cache image initial config")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Pset_mdc_image_config() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5Pget_mdc_image_config
+ *
+ * Purpose:	Retrieve the metadata cache initial image configuration
+ *		from the target FAPL.
+ *
+ *		Observe that the function will fail if config_ptr is
+ *		NULL, or if config_ptr->version specifies an unknown
+ *		version of H5AC_cache_image_config_t.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	J. Mainzer
+ *              Friday, June 26, 2015
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_mdc_image_config(hid_t plist_id, H5AC_cache_image_config_t *config_ptr)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    herr_t ret_value = SUCCEED;   /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE2("e", "i*x", plist_id, config_ptr);
+
+    /* Get the plist structure */
+    if(NULL == (plist = H5P_object_verify(plist_id,H5P_FILE_ACCESS)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* validate the config_ptr */
+    if(config_ptr == NULL)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "NULL config_ptr on entry.")
+
+    if(config_ptr->version != H5AC__CURR_CACHE_IMAGE_CONFIG_VERSION)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "Unknown image config version.")
+
+    /* If we ever support multiple versions of H5AC_cache_config_t, we
+     * will have to get the cannonical version here, and then translate
+     * to the version of the structure supplied.
+     */
+
+    /* Get the current initial metadata cache resize configuration */
+    if(H5P_get(plist, H5F_ACS_META_CACHE_INIT_IMAGE_CONFIG_NAME, config_ptr) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET,FAIL, "can't get metadata cache initial image config")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* H5Pget_mdc_image_config() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5Pset_mdc_config
  *
  * Purpose:	Set the initial metadata cache resize configuration in the
@@ -2754,6 +2868,147 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function: H5P__facc_cache_image_config_cmp
+ *
+ * Purpose: Compare two cache image configurations.
+ *
+ * Return: positive if VALUE1 is greater than VALUE2, negative if VALUE2 is
+ *		greater than VALUE1 and zero if VALUE1 and VALUE2 are equal.
+ *
+ * Programmer:     John Mainzer
+ *                 June 26, 2015
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+H5P__facc_cache_image_config_cmp(const void *_config1, const void *_config2, size_t H5_ATTR_UNUSED size)
+{
+    const H5AC_cache_image_config_t *config1 = (const H5AC_cache_image_config_t *)_config1; /* Create local aliases for values */
+    const H5AC_cache_image_config_t *config2 = (const H5AC_cache_image_config_t *)_config2; /* Create local aliases for values */
+    int ret_value = 0;               /* Return value */
+
+    FUNC_ENTER_STATIC_NOERR
+
+    /* Check for a property being set */
+    if(config1 == NULL && config2 != NULL) HGOTO_DONE(-1);
+    if(config1 != NULL && config2 == NULL) HGOTO_DONE(1);
+
+    if(config1->version < config2->version) HGOTO_DONE(-1);
+    if(config1->version > config2->version) HGOTO_DONE(1);
+
+    if(config1->generate_image < config2->generate_image) HGOTO_DONE(-1);
+    if(config1->generate_image > config2->generate_image) HGOTO_DONE(1);
+
+    if(config1->save_resize_status < config2->save_resize_status) HGOTO_DONE(-1);
+    if(config1->save_resize_status > config2->save_resize_status) HGOTO_DONE(1);
+
+    if(config1->entry_ageout < config2->entry_ageout) HGOTO_DONE(-1);
+    if(config1->entry_ageout > config2->entry_ageout) HGOTO_DONE(1);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5P__facc_cache_image_config_cmp() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:       H5P__facc_cache_image_config_enc
+ *
+ * Purpose:        Callback routine which is called whenever the default
+ *                 cache image config property in the file creation 
+ *		   property list is encoded.
+ *
+ * Return:	   Success:	Non-negative
+ *		   Failure:	Negative
+ *
+ * Programmer:     John Mainzer
+ *                 June 26, 2015
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__facc_cache_image_config_enc(const void *value, void **_pp, size_t *size)
+{
+    const H5AC_cache_image_config_t *config = (const H5AC_cache_image_config_t *)value; /* Create local aliases for value */
+    uint8_t **pp = (uint8_t **)_pp;
+
+    FUNC_ENTER_STATIC_NOERR
+
+    /* Sanity check */
+    HDassert(value);
+
+    if(NULL != *pp) {
+        /* Encode type sizes (as a safety check) */
+        *(*pp)++ = (uint8_t)sizeof(unsigned);
+
+        INT32ENCODE(*pp, (int32_t)config->version);
+
+        H5_ENCODE_UNSIGNED(*pp, config->generate_image);
+
+        H5_ENCODE_UNSIGNED(*pp, config->save_resize_status);
+
+        INT32ENCODE(*pp, (int32_t)config->entry_ageout);
+    } /* end if */
+
+    /* Compute encoded size of fixed-size values */
+    *size += (1 + (2 * sizeof(unsigned)) + (2 * sizeof(int32_t)));
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5P__facc_cache_image_config_enc() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:       H5P__facc_cache_image_config_dec
+ *
+ * Purpose:        Callback routine which is called whenever the default
+ *                 cache image config property in the file creation property 
+ *		   list is  decoded.
+ *
+ * Return:	   Success:	Non-negative
+ *		   Failure:	Negative
+ *
+ * Programmer:     John Mainzer
+ *                 June 26, 2015
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5P__facc_cache_image_config_dec(const void **_pp, void *_value)
+{
+    H5AC_cache_image_config_t *config = (H5AC_cache_image_config_t *)_value;
+    const uint8_t **pp = (const uint8_t **)_pp;
+    unsigned enc_size;
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Sanity checks */
+    HDassert(pp);
+    HDassert(*pp);
+    HDassert(config);
+    HDcompile_assert(sizeof(size_t) <= sizeof(uint64_t));
+
+    /* Set property to default value */
+    HDmemcpy(config, &H5F_def_mdc_initCacheImageCfg_g, sizeof(H5AC_cache_image_config_t));
+
+    /* Decode type sizes */
+    enc_size = *(*pp)++;
+    if(enc_size != sizeof(unsigned))
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "unsigned value can't be decoded")
+
+    INT32DECODE(*pp, config->version);
+
+    H5_DECODE_UNSIGNED(*pp, config->generate_image);
+
+    H5_DECODE_UNSIGNED(*pp, config->save_resize_status);
+
+    INT32DECODE(*pp, config->entry_ageout);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5P__facc_cache_image_config_dec() */
+
+
+/*-------------------------------------------------------------------------
  * Function:    H5P__facc_file_image_info_set
  *
  * Purpose:     Copies a file image property when it's set for a property list
diff --git a/src/H5Ppublic.h b/src/H5Ppublic.h
index c736d7b..5aa8301 100644
--- a/src/H5Ppublic.h
+++ b/src/H5Ppublic.h
@@ -365,6 +365,8 @@ H5_DLL herr_t H5Pget_all_coll_metadata_ops(hid_t plist_id, hbool_t *is_collectiv
 H5_DLL herr_t H5Pset_coll_metadata_write(hid_t plist_id, hbool_t is_collective);
 H5_DLL herr_t H5Pget_coll_metadata_write(hid_t plist_id, hbool_t *is_collective);
 #endif /* H5_HAVE_PARALLEL */
+H5_DLL herr_t H5Pset_mdc_image_config(hid_t plist_id, H5AC_cache_image_config_t *config_ptr);
+H5_DLL herr_t H5Pget_mdc_image_config(hid_t plist_id, H5AC_cache_image_config_t *config_ptr /*out*/);
 
 /* Dataset creation property list (DCPL) routines */
 H5_DLL herr_t H5Pset_layout(hid_t plist_id, H5D_layout_t layout);
diff --git a/src/Makefile.am b/src/Makefile.am
index 939e151..69b54b4 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -46,7 +46,8 @@ libhdf5_la_SOURCES= H5.c H5checksum.c H5dbg.c H5system.c H5timer.c H5trace.c \
         H5B.c H5Bcache.c H5Bdbg.c \
         H5B2.c H5B2cache.c H5B2dbg.c H5B2hdr.c H5B2int.c H5B2internal.c \
         H5B2leaf.c H5B2stat.c H5B2test.c \
-        H5C.c H5Cdbg.c H5Cepoch.c H5Clog.c H5Cquery.c H5Ctag.c H5Ctest.c \
+        H5C.c H5Cdbg.c H5Cepoch.c H5Cimage.c H5Clog.c H5Cprefetched.c \
+        H5Cquery.c H5Ctag.c H5Ctest.c \
         H5CS.c \
         H5D.c H5Dbtree.c H5Dbtree2.c H5Dchunk.c H5Dcompact.c H5Dcontig.c H5Ddbg.c \
         H5Ddeprec.c H5Dearray.c H5Defl.c H5Dfarray.c H5Dfill.c H5Dint.c \
@@ -81,7 +82,8 @@ libhdf5_la_SOURCES= H5.c H5checksum.c H5dbg.c H5system.c H5timer.c H5trace.c \
         H5MF.c H5MFaggr.c H5MFdbg.c H5MFsection.c \
         H5MM.c H5MP.c H5MPtest.c \
         H5O.c H5Oainfo.c H5Oalloc.c H5Oattr.c \
-        H5Oattribute.c H5Obogus.c H5Obtreek.c H5Ocache.c H5Ochunk.c \
+        H5Oattribute.c H5Obogus.c H5Obtreek.c H5Ocache.c H5Ocache_image.c \
+        H5Ochunk.c \
         H5Ocont.c H5Ocopy.c H5Odbg.c H5Odrvinfo.c H5Odtype.c H5Oefl.c \
         H5Ofill.c H5Oflush.c H5Ofsinfo.c H5Oginfo.c \
         H5Olayout.c \