Re: Strange write behavior on an osd

["João Eduardo Luís" <jecluis@gmail.com>]

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On 04/24/2012 05:06 PM, Martin Mailand wrote:
> Hi,
> 
> Am 24.04.2012 17:23, schrieb João Eduardo Luís:
>> Any chance you could run iotop during the busy periods and tell us which
>> processes are issuing the io?
> 
> sure,
> http://85.214.49.87/ceph/iotop.txt
> 
> -martin
> 

I don't want to rush into a definite answer, but it looks like the IO
bursts are caused by btrfs. The periods on which they happen are
consistent with btrfs' internal thread scheduling (which are fired every
30 seconds), and from iotop it would seem as if they're the ones
responsible for all the IO when it jumps from the "couple of MB/s" mark
to "several hundreds of MB/s".

I've seen it happen before, although on synthetic and very specific
workloads. Not sure on what may be the cause in your case though.

What kernel and btrfs versions are you using?

-- 
João Eduardo Luís
gpg key: 477C26E5 from pool.keyserver.eu


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