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List:       ceph-devel
Subject:    Re: ceph mgr balancer bad distribution
From:       Stefan Priebe - Profihost AG <s.priebe () profihost ! ag>
Date:       2018-02-28 13:59:55
Message-ID: f8725c11-a083-2f05-dc0d-5d2a5517534e () profihost ! ag
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Am 28.02.2018 um 13:58 schrieb Dan van der Ster:
> Hi Stefan,
> 
> Which balancer mode are you using? crush-compat scores using a mix of
> nobjects, npgs, and size. It's doing pretty well over here as long as
> you have a relatively small number of empty PGs.
>
> I believe that upmap uses nPGs only, and I haven't tested it enough
> yet to know if it actually improves things.
> 
> Also, did you only run one iteration of the balancer? It only moves up
> to 5% of objects each iteration, so it can take several to fully
> balance things.

crush-compat mode

Yes only one iteration but i set max_misplaced to 20%:
    "mgr/balancer/max_misplaced": "20.00",

> 
> -- dan
> 
> 
> On Wed, Feb 28, 2018 at 1:47 PM, Stefan Priebe - Profihost AG
> <s.priebe@profihost.ag> wrote:
>> Hello,
>>
>> with jewel we always used the python crush optimizer which gave us a
>> pretty good distribution fo the used space.
>>
>> Since luminous we're using the included ceph mgr balancer but the
>> distribution is far from perfect and much worse than the old method.
>>
>> Is there any way to tune the mgr balancer?
>>
>> Currently after a balance we still have:
>> 75% to 92% disk usage which is pretty unfair
>>
>> Greets,
>> Stefan
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