From: Lars Marowsky-Bree Date: Wed, 31 Jul 2019 13:12:49 +0000 (+0200) Subject: doc: Address further comments on choosing pg_num X-Git-Tag: v15.1.0~1996^2 X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=3a7e171df6b8a01197ff02a190f9f6e97e0d6627;p=ceph-ci.git doc: Address further comments on choosing pg_num Signed-off-by: Lars Marowsky-Bree --- diff --git a/doc/rados/operations/placement-groups.rst b/doc/rados/operations/placement-groups.rst index 8006d77e0d7..d5cc267c27d 100644 --- a/doc/rados/operations/placement-groups.rst +++ b/doc/rados/operations/placement-groups.rst @@ -434,11 +434,12 @@ You should then check if the result makes sense with the way you designed your Ceph cluster to maximize `data durability`_, `object distribution`_ and minimize `resource usage`_. -The result should always be **rounded up to the nearest power of two.** -A power of two will evenly balance the number of objects among placement groups. -You could set it to a different value but you should be aware that this could result in -an uneven distribution of data across your OSDs. Use of such values shoud be limited to -incrementally stepping from one power of two to another. +The result should always be **rounded up to the nearest power of two**. + +Only a power of two will evenly balance the number of objects among +placement groups. Other values will result in an uneven distribution of +data across your OSDs. Their use should be limited to incrementally +stepping from one power of two to another. As an example, for a cluster with 200 OSDs and a pool size of 3 replicas, you would estimate your number of PGs as follows::