Adjusting the cluster map size

Adjusting the cluster map size in the Ceph configuration can help reduce memory consumption, when needed.

By default, the ceph-osd daemon caches 500 previous osdmaps. Even with deduplication, the map might consume a lot of memory per daemon. Tuning the cache size in the Ceph configuration might help reduce memory consumption significantly. For example:

[ceph: root@host01 /]# ceph config set global osd_map_message_max 10
[ceph: root@host01 /]# ceph config set osd osd_map_cache_size 20
[ceph: root@host01 /]# ceph config set osd osd_map_share_max_epochs 10
[ceph: root@host01 /]# ceph config set osd osd_pg_epoch_persisted_max_stale 10

The ceph-manager daemon handles PG queries, so the cluster map should not impact performance.