Appendix E. Pools, placement groups, and CRUSH configuration options The Ceph options that govern pools, placement groups, and the CRUSH algorithm. Configuration option Description Type Default mon_allow_pool_delete Allows a monitor to delete a pool. In RHCS 3 and later releases, the monitor cannot delete the pool by default as an added measure to protect data. Boolean false mon_max_pool_pg_num The maximum number of placement groups per pool. Integer 65536 mon_pg_create_interval Number of seconds between PG creation in the same Ceph OSD Daemon. Float 30.0 mon_pg_stuck_threshold Number of seconds after which PGs can be considered as being stuck. 32-bit Integer 300 mon_pg_min_inactive Ceph issues a HEALTH_ERR status in the cluster log if the number of PGs that remain inactive longer than the mon_pg_stuck_threshold exceeds this setting. The default setting is one PG. A non-positive number disables this setting. Integer 1 mon_pg_warn_max_per_osd Ceph issues a HEALTH_WARN status in the cluster log if the average number of PGs per OSD in the cluster is greater than this setting. A non-positive number disables this setting. Integer 300 mon_pg_warn_min_per_osd Ceph issues a HEALTH_WARN status in the cluster log if the average number of PGs per OSD in the cluster is less than this setting. A non-positive number disables this setting. Integer 30 mon_pg_warn_min_objects Do not warn if the total number of objects in the cluster is below this number. Integer 1000 mon_pg_warn_min_pool_objects Do not warn on pools whose object number is below this number. Integer 1000 mon_pg_check_down_all_threshold The threshold of down OSDs by percentage after which Ceph checks all PGs to ensure they are not stuck or stale. Float 0.5 mon_pg_warn_max_object_skew Ceph issue a HEALTH_WARN status in the cluster log if the average number of objects in a pool is greater than mon pg warn max object skew times the average number of objects for all pools. A non-positive number disables this setting. Float 10 mon_delta_reset_interval The number of seconds of inactivity before Ceph resets the PG delta to zero. Ceph keeps track of the delta of the used space for each pool to aid administrators in evaluating the progress of recovery and performance. Integer 10 mon_osd_max_op_age The maximum age in seconds for an operation to complete before issuing a HEALTH_WARN status. Float 32.0 osd_pg_bits Placement group bits per Ceph OSD Daemon. 32-bit Integer 6 osd_pgp_bits The number of bits per Ceph OSD Daemon for Placement Groups for Placement purpose (PGPs). 32-bit Integer 6 osd_crush_chooseleaf_type The bucket type to use for chooseleaf in a CRUSH rule. Uses ordinal rank rather than name. 32-bit Integer 1 . Typically a host containing one or more Ceph OSD Daemons. osd_pool_default_crush_replicated_ruleset The default CRUSH ruleset to use when creating a replicated pool. 8-bit Integer 0 osd_pool_erasure_code_stripe_unit Sets the default size, in bytes, of a chunk of an object stripe for erasure coded pools. Every object of size S will be stored as N stripes, with each data chunk receiving stripe unit bytes. Each stripe of N * stripe unit bytes will be encoded/decoded individually. This option can be overridden by the stripe_unit setting in an erasure code profile. Unsigned 32-bit Integer 4096 osd_pool_default_size Sets the number of replicas for objects in the pool. The default value is the same as ceph osd pool set {pool-name} size {size} . 32-bit Integer 3 osd_pool_default_min_size Sets the minimum number of written replicas for objects in the pool in order to acknowledge a write operation to the client. If the minimum is not met, Ceph will not acknowledge the write to the client. This setting ensures a minimum number of replicas when operating in degraded mode. 32-bit Integer 0 , which means no particular minimum. If 0 , minimum is size - (size / 2) . osd_pool_default_pg_num The default number of placement groups for a pool. The default value is the same as pg_num with mkpool . 32-bit Integer 32 osd_pool_default_pgp_num The default number of placement groups for placement for a pool. The default value is the same as pgp_num with mkpool . PG and PGP should be equal. 32-bit Integer 0 osd_pool_default_flags The default flags for new pools. 32-bit Integer 0 osd_max_pgls The maximum number of placement groups to list. A client requesting a large number can tie up the Ceph OSD Daemon. Unsigned 64-bit Integer 1024 osd_min_pg_log_entries The minimum number of placement group logs to maintain when trimming log files. 32-bit Int Unsigned 250 osd_default_data_pool_replay_window The time, in seconds, for an OSD to wait for a client to replay a request. 32-bit Integer 45

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