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documentation: adapt PG formula for erasure coded pools

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Signed-off-by: Loic Dachary <loic@dachary.org>
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Loic Dachary 2014-05-23 07:25:37 +02:00
parent 04f8e0effa
commit ab0db34eaa
1 changed files with 7 additions and 3 deletions
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10
doc/rados/operations/placement-groups.rst
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@ -43,9 +43,13 @@ across your cluster. We recommend approximately 50-100 placement groups per OSD
to balance out memory and CPU requirements and per-OSD load. For a single pool
of objects, you can use the following formula::
(OSDs * 100)
Total PGs = ------------
Replicas
(OSDs * 100)
Total PGs = ------------
OSD per object
Where **OSD per object** is the number of replicas (or pool size) for
replicated pools or the K+M sum for erasure coded pools (as returned
by **ceph osd erasure-code-profile get**).
The result should be **rounded up to the nearest power of two.**
Rounding up is optional, but recommended if you want to ensure that