From: Anthony D'Atri Date: Wed, 23 Jun 2021 17:25:13 +0000 (-0700) Subject: doc/rados/operations: Updates pools.rst X-Git-Tag: v17.1.0~1570^2 X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=refs%2Fpull%2F41994%2Fhead;p=ceph.git doc/rados/operations: Updates pools.rst Add clarity, change example PG counts to a power of two. Signed-off-by: Anthony D'Atri --- diff --git a/doc/rados/operations/pools.rst b/doc/rados/operations/pools.rst index 191ade928d23e..82cfaddd82901 100644 --- a/doc/rados/operations/pools.rst +++ b/doc/rados/operations/pools.rst @@ -8,16 +8,20 @@ pools for storing data. A pool provides you with: - **Resilience**: You can set how many OSD are allowed to fail without losing data. For replicated pools, it is the desired number of copies/replicas of an object. - A typical configuration stores an object and one additional copy - (i.e., ``size = 2``), but you can determine the number of copies/replicas. + A typical configuration stores an object and two additional copies + (i.e., ``size = 3``), but you can configure the number of copies/replicas at + pool granularity. For `erasure coded pools <../erasure-code>`_, it is the number of coding chunks (i.e. ``m=2`` in the **erasure code profile**) - **Placement Groups**: You can set the number of placement groups for the pool. - A typical configuration uses approximately 100 placement groups per OSD to + A typical configuration targets approximately 100 placement groups per OSD to provide optimal balancing without using up too many computing resources. When - setting up multiple pools, be careful to ensure you set a reasonable number of - placement groups for both the pool and the cluster as a whole. + setting up multiple pools, be careful to set a reasonable number of + placement groups for each pool and for the cluster as a whole. Note that each PG + belongs to a specific pool, so when multiple pools use the same OSDs, you must + take care that the **sum** of PG replicas per OSD is in the desired PG per OSD + target range. - **CRUSH Rules**: When you store data in a pool, placement of the object and its replicas (or chunks for erasure coded pools) in your cluster is governed @@ -62,8 +66,8 @@ For details on placement group numbers refer to `setting the number of placement For example:: - osd pool default pg num = 100 - osd pool default pgp num = 100 + osd_pool_default_pg_num = 128 + osd_pool_default_pgp_num = 128 To create a pool, execute::