mimic: core: mon osdmap cash too small during upgrade to mimic

PendingReleaseNotes

@@ -36,6 +36,14 @@ notes (?))
 13.2.3
 ======
 
+* The default memory utilization for the mons has been increased
+  somewhat.  Rocksdb now uses 512 MB of RAM by default, which should
+  be sufficient for small to medium-sized clusters; large clusters
+  should tune this up.  Also, the ``mon_osd_cache_size`` has been
+  increase from 10 OSDMaps to 500, which will translate to an
+  additional 500 MB to 1 GB of RAM for large clusters, and much less
+  for small clusters.
+
 * Ceph v13.2.2 includes a wrong backport, which may cause mds to go into
   'damaged' state when upgrading Ceph cluster from previous version.
   The bug is fixed in v13.2.3. For ceph v13.2.2 installation, upgrading

doc/start/hardware-recommendations.rst

@@ -39,11 +39,29 @@ separate hosts.
 RAM
 ===
 
-Metadata servers and monitors must be capable of serving their data quickly, so
-they should have plenty of RAM (e.g., 1GB of RAM per daemon instance). OSDs do
-not require as much RAM for regular operations (e.g., 500MB of RAM per daemon
-instance); however, during recovery they need significantly more RAM (e.g., ~1GB
-per 1TB of storage per daemon). Generally, more RAM is better.
+Generally, more RAM is better.
+
+Monitors and managers (ceph-mon and ceph-mgr)
+---------------------------------------------
+
+Monitor and manager daemon memory usage generally scales with the size of the
+cluster.  For small clusters, 1-2 GB is generally sufficient.  For
+large clusters, you should provide more (5-10 GB).  You may also want
+to consider tuning settings like ``mon_osd_cache_size`` or
+``rocksdb_cache_size``.
+
+Metadata servers (ceph-mds)
+---------------------------
+
+The metadata daemon memory utilization depends on how much memory its cache is
+configured to consume.  We recommend 1 GB as a minimum for most systems.  See
+``mds_cache_memory``.
+
+OSDs (ceph-osd)
+---------------
+
+By default, OSDs that use the BlueStore backend require 3-5 GB of RAM.  You can
+adjust the amount of memory the OSD consumes with the ``osd_memory_target`` configuration option when BlueStore is in use.  When using the legacy FileStore backend, the operating system page cache is used for caching data, so no tuning is normally needed, and the OSD memory consumption is generally related to the number of PGs per daemon in the system.
 
 
 Data Storage

src/common/options.cc

@@ -1184,7 +1184,7 @@ std::vector<Option> get_global_options() {
     /* -- mon: osdmap prune (end) -- */
 
     Option("mon_osd_cache_size", Option::TYPE_INT, Option::LEVEL_ADVANCED)
-    .set_default(10)
+    .set_default(500)
     .set_description(""),
 
     Option("mon_cpu_threads", Option::TYPE_INT, Option::LEVEL_ADVANCED)
@@ -3423,7 +3423,7 @@ std::vector<Option> get_global_options() {
     .set_description(""),
 
     Option("rocksdb_cache_size", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
-    .set_default(128_M)
+    .set_default(512_M)
     .set_description(""),
 
     Option("rocksdb_cache_row_ratio", Option::TYPE_FLOAT, Option::LEVEL_ADVANCED)