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Pool&PG&CRUSH配置.md

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Pool & PG & CRUSH 配置

官方文档：https://ceph.readthedocs.io/en/latest/rados/configuration/pool-pg-config-ref/

创建 Pool 并设置 Pool 的 PG 数时，当没有明确覆盖默认值时，Ceph将使用默认值。建议覆盖一些默认设置。具体来说，建议设置 Pool 的副本大小，并覆盖默认的 PG 数。可以在运行 Pool 命令时专门设置这些值。还可以通过在 Ceph 配置文件的 [global] 部分添加新的默认值来覆盖默认值。

[global]

	# By default, Ceph makes 3 replicas of objects. If you want to make four
	# copies of an object the default value--a primary copy and three replica
	# copies--reset the default values as shown in 'osd pool default size'.
	# If you want to allow Ceph to write a lesser number of copies in a degraded
	# state, set 'osd pool default min size' to a number less than the
	# 'osd pool default size' value.

	osd pool default size = 3  # Write an object 3 times.
	osd pool default min size = 2 # Allow writing two copies in a degraded state.

	# Ensure you have a realistic number of placement groups. We recommend
	# approximately 100 per OSD. E.g., total number of OSDs multiplied by 100
	# divided by the number of replicas (i.e., osd pool default size). So for
	# 10 OSDs and osd pool default size = 4, we'd recommend approximately
	# (100 * 10) / 4 = 250.
        # always use the nearest power of 2

	osd pool default pg num = 256
	osd pool default pgp num = 256

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

    Issue a HEALTH_ERR in cluster log if the number of PGs stay inactive longer than mon_pg_stuck_threshold exceeds this setting. A non-positive number means disabled, never go into ERR.

  • Type：Integer

  • Default：1

mon pg warn min per osd

  • Description

    Issue a HEALTH_WARN in cluster log if the average number of PGs per (in) OSD is under this number. (a non-positive number disables this)

  • Type：Integer

  • Default：30

mon pg warn min objects

  • Description

    Do not warn if the total number of objects in 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

    Threshold of down OSDs percentage after which we check all PGs for stale ones.

  • Type：Float

  • Default：0.5

mon pg warn max object skew

  • Description

    Issue a HEALTH_WARN in cluster log if the average object number of a certain pool is greater than mon pg warn max object skew times the average object number of the whole pool. (zero or a non-positive number disables this). Note that this option applies to the managers.

  • Type：Float

  • Default：10

mon delta reset interval

  • Description

    Seconds of inactivity before we reset the pg delta to 0. We keep track of the delta of the used space of each pool, so, for example, it would be easier for us to understand the progress of recovery or the performance of cache tier. But if there’s no activity reported for a certain pool, we just reset the history of deltas of that pool.

  • Type：Integer

  • Default：10

mon osd max op age

  • Description

    Maximum op age before we get concerned (make it a power of 2). A HEALTH_WARN will be issued if a request has been blocked longer than this limit.

  • 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 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 crush initial weight

  • Description

    The initial crush weight for newly added osds into crushmap.

  • Type：Double

  • Default

    the size of newly added osd in TB. By default, the initial crush weight for the newly added osd is set to its volume size in TB. See Weighting Bucket Items for details.

osd pool default crush rule

  • Description

    The default CRUSH rule to use when creating a replicated pool.

  • Type：8-bit Integer

  • Default

    -1, which means “pick the rule with the lowest numerical ID and use that”. This is to make pool creation work in the absence of rule 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, which may result in data loss. 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：32

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 (for now).

  • 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：250

osd max pg log entries

  • Description

    The maximum number of placement group logs to maintain when trimming log files.

  • Type：32-bit Int Unsigned

  • Default：10000

osd default data pool replay window

  • Description

    The time (in seconds) for an OSD to wait for a client to replay a request.

  • Type：32-bit Integer

  • Default：45

osd max pg per osd hard ratio

  • Description

    The ratio of number of PGs per OSD allowed by the cluster before OSD refuses to create new PGs. OSD stops creating new PGs if the number of PGs it serves exceeds osd max pg per osd hard ratio * mon max pg per osd.

  • Type：Float

  • Default：2

osd recovery priority

  • Description

    Priority of recovery in the work queue.

  • Type：Integer

  • Default：5

osd recovery op priority

  • Description

    Default priority used for recovery operations if pool doesn’t override.

  • Type：Integer

  • Default：3