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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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