You should have settled with the nearest power of 2, which for 666 is
512. Since you created the cluster and IIRC is a testbed, you may as
well recreate it again, however it will less of a hassle to just
increase the pgs to the next power of two: 1024
Your 20 ods appear to be equal sized in your crushmap so ~150pgs / osd
should still be acceptable.
Hope you nail it this time :)
-K.
On 03/23/2016 01:10 PM, Zhang Qiang wrote:
> Oliver, Goncalo,
>
> Sorry to disturb again, but recreating the pool with a smaller pg_num
> didn't seem to work, now all 666 pgs are degraded + undersized.
>
> New status:
> cluster d2a69513-ad8e-4b25-8f10-69c4041d624d
> health HEALTH_WARN
> 666 pgs degraded
> 82 pgs stuck unclean
> 666 pgs undersized
> monmap e5: 5 mons at
>
{1=10.3.138.37:6789/0,2=10.3.138.39:6789/0,3=10.3.138.40:6789/0,4=10.3.138.59:6789/0,GGZ-YG-S0311-PLATFORM-138=10.3.138.36:6789/0
>
<http://10.3.138.37:6789/0,2=10.3.138.39:6789/0,3=10.3.138.40:6789/0,4=10.3.138.59:6789/0,GGZ-YG-S0311-PLATFORM-138=10.3.138.36:6789/0>}
> election epoch 28, quorum 0,1,2,3,4
> GGZ-YG-S0311-PLATFORM-138,1,2,3,4
> osdmap e705: 20 osds: 20 up, 20 in
> pgmap v1961: 666 pgs, 1 pools, 0 bytes data, 0 objects
> 13223 MB used, 20861 GB / 21991 GB avail
> 666 active+undersized+degraded
>
> Only one pool and its size is 3. So I think according to the algorithm,
> (20 * 100) / 3 = 666 pgs is reasonable.
>
> I updated health detail and also attached a pg query result on
> gist(https://gist.github.com/dotSlashLu/22623b4cefa06a46e0d4).
>
> On Wed, 23 Mar 2016 at 09:01 Dotslash Lu <dotslash.lu@xxxxxxxxx
> <mailto:dotslash.lu@xxxxxxxxx>> wrote:
>
> Hello Gonçalo,
>
> Thanks for your reminding. I was just setting up the cluster for
> test, so don't worry, I can just remove the pool. And I learnt that
> since the replication number and pool number are related to pg_num,
> I'll consider them carefully before deploying any data.
>
> On Mar 23, 2016, at 6:58 AM, Goncalo Borges
> <goncalo.borges@xxxxxxxxxxxxx <mailto:goncalo.borges@xxxxxxxxxxxxx>>
> wrote:
>
>> Hi Zhang...
>>
>> If I can add some more info, the change of PGs is a heavy
>> operation, and as far as i know, you should NEVER decrease PGs.
>> From the notes in pgcalc (http://ceph.com/pgcalc/):
>>
>> "It's also important to know that the PG count can be increased,
>> but NEVER decreased without destroying / recreating the pool.
>> However, increasing the PG Count of a pool is one of the most
>> impactful events in a Ceph Cluster, and should be avoided for
>> production clusters if possible."
>>
>> So, in your case, I would consider in adding more OSDs.
>>
>> Cheers
>> Goncalo
>
>
>
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