Re: ceph from poc to production

[Mark Nelson <mark.nelson@inktank.com>]

On 01/17/2013 10:24 AM, Sébastien Han wrote:
> Hi Stephan,
>
>> - Increase the osdmax value
>
> Well actually this doesn't seem to be necessary because when you issue
> a "ceph osd create" the osdmax value is automatically incremented. It
> just that a while ago I saw on the ML or IRC that it was a good
> practice to do this. And this documentation
> http://ceph.com/docs/master/rados/operations/control/ says:
>
> "Set the max_osd parameter in the osd map. This is necessary when
> expanding the storage cluster."
>
> Maybe the doc is outdated on this option, I don't know.
>
>> - Set “filestore flusher” option to false, in your [osd] section
>
> During my benchmarks sessions I noticed that disabling this option
> brought way better performance, at least for old hardware. Fo recent
> hardware I haven't seen any difference, but I kept the habit to
> disable it. There are some discussions about this option on the ML. As
> far as I can remember, it's harmless to disable it.
>  From the doc here
> http://ceph.com/docs/master/rados/configuration/filestore-config-ref/:

I actually have been doing parametric sweeps over the various ceph 
tunables to try to see what affects performance.  I'll have an article 
coming out soonish documenting some of the findings.  Typically 
disabling the flusher seems to be beneficial on XFS and BTRFS, but it 
seems to be the opposite on EXT4.

>
> "The filestore flusher forces data from large writes to be written out
> using sync file range before the sync in order to (hopefully) reduce
> the cost of the eventual sync. In practice, disabling ‘filestore
> flusher’ seems to improve performance in some cases."
>
> Cheers,
>
> --
> Regards,
> Sébastien Han.
>
>
> On Wed, Jan 16, 2013 at 7:41 PM, Stefan Priebe <s.priebe@profihost.ag> wrote:
>>
>> Hello Sebastien,
>>    hello list,
>>
>> first nice article sebastien ;-) thanks for contributing.
>>
>> I've two question regarding the tips:
>>
>> Can somebody explain me why i should do this?:
>> - Increase the osdmax value
>> - Set “filestore flusher” option to false, in your [osd] section
>>
>> Greets,
>> Stefan
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