diff --git a/doc/rados/operations/pools.rst b/doc/rados/operations/pools.rst index 62623b491ba..fc82510fa4b 100644 --- a/doc/rados/operations/pools.rst +++ b/doc/rados/operations/pools.rst @@ -50,6 +50,14 @@ The default pools include: Create a Pool ============= +Before creating pools, refer to the `Pool, PG and CRUSH Config Reference`_. +Ideally, you should override the default value for the number of placement +groups in you Ceph configuration file, as the default is NOT ideal. +For example:: + + osd pool default pg num = 100 + osd pool default pgp num = 100 + To create a pool, execute:: ceph osd pool create {pool-name} {pg-num} [{pgp-num}] @@ -60,7 +68,7 @@ Where: :Description: The name of the pool. It must be unique. :Type: String -:Required: Yes +:Required: Yes. Picks up default or Ceph configuration value if not specified. ``{pg-num}`` @@ -79,9 +87,10 @@ Where: for placement group splitting scenarios. :Type: Integer -:Required: Yes +:Required: Yes. Picks up default or Ceph configuration value if not specified. :Default: 8 + When you create a pool, set the number of placement groups to a reasonable value (e.g., ``100``). Consider the total number of placement groups per OSD too. Placement groups are computationally expensive, so performance will degrade when @@ -230,19 +239,15 @@ For example:: ceph osd pool set data size 3 -You may execute this command for each pool. - -Note, however, that pool size is more of a best-effort setting: an object -might accept ios in degraded mode with fewer than size replicas. To -set a minimum number of required replicas for io, you should use the -min_size setting. - +You may execute this command for each pool. **Note:** An object might accept +I/Os in degraded mode with fewer than ``pool size`` replicas. To set a minimum +number of required replicas for I/O, you should use the ``min_size`` setting. For example:: ceph osd pool set data min_size 2 -This ensures that no object in the data pool will receive io with fewer than -min_size replicas. +This ensures that no object in the data pool will receive I/O with fewer than +``min_size`` replicas. Get the Number of Object Replicas @@ -253,4 +258,9 @@ To get the number of object replicas, execute the following:: ceph osd dump | grep 'rep size' Ceph will list the pools, with the ``rep size`` attribute highlighted. -By default, Ceph creates two replicas of an object (two copies). +By default, ceph Creates one replica of an object (a total of two copies, or +a size of 2). + + + +.. _Pool, PG and CRUSH Config Reference: ../../configuration/pool-pg-config-ref