Appendix E. Pools, placement groups and CRUSH configuration options The Ceph options that govern pools, placement groups, and the CRUSH algorithm. mon_allow_pool_delete Description 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. Type Boolean Default false mon_max_pool_pg_num Description The maximum number of placement groups per pool. Type Integer Default 65536 mon_pg_create_interval Description Number of seconds between PG creation in the same Ceph OSD Daemon. Type Float Default 30.0 mon_pg_stuck_threshold Description Number of seconds after which PGs can be considered as being stuck. Type 32-bit Integer Default 300 mon_pg_min_inactive Description 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. Type Integer Default 1 mon_pg_warn_min_per_osd Description 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. Type Integer Default 30 mon_pg_warn_max_per_osd Description 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. Type Integer Default 300 mon_pg_warn_min_objects Description Do not warn if the total number of objects in the cluster is below this number. Type Integer Default 1000 mon_pg_warn_min_pool_objects Description Do not warn on pools whose object number is below this number. Type Integer Default 1000 mon_pg_check_down_all_threshold Description The threshold of down OSDs by percentage after which Ceph checks all PGs to ensure they are not stuck or stale. Type Float Default 0.5 mon_pg_warn_max_object_skew Description 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. Type Float Default 10 mon_delta_reset_interval Description 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. Type Integer Default 10 mon_osd_max_op_age Description The maximimum age in seconds for an operation to complete before issuing a HEALTH_WARN status. Type Float Default 32.0 osd_pg_bits Description Placement group bits per Ceph OSD Daemon. Type 32-bit Integer Default 6 osd_pgp_bits Description The number of bits per Ceph OSD Daemon for Placement Groups for Placement purpose (PGPs). Type 32-bit Integer Default 6 osd_crush_chooseleaf_type Description The bucket type to use for chooseleaf in a CRUSH rule. Uses ordinal rank rather than name. Type 32-bit Integer Default 1 . Typically a host containing one or more Ceph OSD Daemons. osd_pool_default_crush_replicated_ruleset Description The default CRUSH ruleset to use when creating a replicated pool. Type 8-bit Integer Default 0 osd_pool_erasure_code_stripe_unit Description 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 is overridden by the stripe_unit setting in an erasure code profile. Type Unsigned 32-bit Integer Default 4096 osd_pool_default_size Description 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} . Type 32-bit Integer Default 3 osd_pool_default_min_size Description Sets the minimum number of written replicas for objects in the pool in order to acknowledge a write operation to the client. If 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. Type 32-bit Integer Default 0 , which means no particular minimum. If 0 , minimum is size - (size / 2) . osd_pool_default_pg_num Description The default number of placement groups for a pool. The default value is the same as pg_num with mkpool . Type 32-bit Integer Default 8 osd_pool_default_pgp_num Description 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. Type 32-bit Integer Default 8 osd_pool_default_flags Description The default flags for new pools. Type 32-bit Integer Default 0 osd_max_pgls Description The maximum number of placement groups to list. A client requesting a large number can tie up the Ceph OSD Daemon. Type Unsigned 64-bit Integer Default 1024 Note Default should be fine. osd_min_pg_log_entries Description The minimum number of placement group logs to maintain when trimming log files. Type 32-bit Int Unsigned Default 1000 osd_deep_scrub_large_omap_object_value_sum_threshold Description Sets a threshold value for number of omap keys that a RADOS object may have. If the number of omap keys exceeds the threshold value, the placement group that contains the RADOS object logs messages when the group is deep-scrubbed. One message is logged to the cluster log ceph.log . It includes the warning cluster [WRN] Large omap object found , the key count, and the size of the object in bytes. The second message adds the cluster status message Large OMAP count to HEALTH_WARN. For more information, refer to link:https://access.redhat.com/solutions/3660171 Type 64-bit Unsigned Integer Default 20000

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