----- Message from Loic Dachary <l...@dachary.org> ---------
Date: Fri, 23 May 2014 07:37:22 +0200
From: Loic Dachary <l...@dachary.org>
Subject: Re: [ceph-users] recommendations for erasure coded pools and
profile question
To: Kenneth Waegeman <kenneth.waege...@ugent.be>, ceph-users
<ceph-users@lists.ceph.com>
Hi Kenneth,
In the case of erasure coded pools, the "Replicas" should be
replaced by "K+M".
$ ceph osd erasure-code-profile get myprofile
k=2
m=1
plugin=jerasure
technique=reed_sol_van
ruleset-failure-domain=osd
You have K+M=3
I proposed a fix to the documentation
https://github.com/ceph/ceph/pull/1856 . If I understand correctly,
this formula is more a helper than an exact count, otherwise it
would be embedded into Ceph and the operator would not have to think
about it.
Thanks Loic also for this!
Since it is not an exact count, in which situations should we not use
this formula? I guess mainly when planning to add more pools on the
same OSDs (and thus 'saving' PGs for future use). Are there other
considerations?
Also, inside Ceph, when using only/mainly EC pools, I get a health warning :
HEALTH_WARN too few pgs per osd (15 < min 20), which is indeed true
when e.g having only one EC pool with eg K+M=10:
Total PGs = OSD * 100 / 10 -> 10 PGs per OSD. Should we ignore this?
Cheers!
Kenneth
ceph --format json osd dump
will show you which pool is using which profile.
Cheers
On 22/05/2014 14:38, Kenneth Waegeman wrote:
Hi,
How can we apply the recommendations of the number of placement
groups onto erasure-coded pools?
(OSDs * 100)
Total PGs = ------------
Replicas
Should we set replica = 1, or should it be set against some EC parameters?
Also a question about the EC profiles.
I know you can show them with 'ceph osd erasure-code-profile ls',
get or set parameters with 'ceph osd erasure-code-profile get/set',
and create a pool with it with 'ceph osd create ecpool pg pgn
erasure <profile>. But can you also list which pool has which
profile?
Thanks!
Kenneth
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--
Loïc Dachary, Artisan Logiciel Libre
----- End message from Loic Dachary <l...@dachary.org> -----
--
Met vriendelijke groeten,
Kenneth Waegeman
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