From: Tomas Vondra <tv@fuzzy.cz>
To: Andy Colson <andy@squeakycode.net>
Cc: Tomas Vondra <tv@fuzzy.cz>
Cc: Gerhard Wohlgenannt <wohlg@ai.wu.ac.at>
Cc: pgsql-performance@postgresql.org, "Heinz-Peter Lang" <heinz@langatium.net>
Cc: Gerhard Wohlgenannt <wohlg@ai.wu-wien.ac.at>
Cc: Weichselbraun, Albert <albert.weichselbraun@wu.ac.at>
Subject: Re: Sudden drop in DBb performance
Date: Mon, 5 Sep 2011 16:15:23 +0200
Message-ID: <785367bd0412b17bcd89350bcd703de6.squirrel@sq.gransy.com> (raw)
In-Reply-To: <4E64D3D3.8000205@squeakycode.net>
References: <4E61D6B4.9090804@ai.wu.ac.at>
<33fadeb6ac1bade5ef01bd08d1fd7807.squirrel@sq.gransy.com>
<4E64D3D3.8000205@squeakycode.net>
On 5 Září 2011, 15:51, Andy Colson wrote:
> On 09/05/2011 02:48 AM, Tomas Vondra wrote:
>> That seems a bit slow ... 27MB/s for writes and 41MB/s forreads is ait
>> slow with 8 drives.
>>
>> Tomas
>>
>>
>
> Agreed, that's really slow. A single SATA drive will get 60 MB/s. Did
> you run Bonnie while the VM's were up and running?
>
> root@host:~# vmstat
> procs -----------memory---------- ---swap-- -----io---- -system--
> ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy
> id wa
> 0 0 0 308024 884812 40512932 0 0 464 168 353 92 4
> 2 84 9
>
>
> Only one line? That does not help much. Can you run it as 'vmstat 2' and
> let it run while a few slow queries are performed? Then paste all the
> lines?
And maybe a few lines from "iostat -x 2" too.
BTW what kind of raid is it? Is it hw or sw based? Have you checked health
of the drives?
Are you sure there's nothing else using the drives (e.g. one of the VMs,
rebuild of the array or something like that)?
Tomas
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To: pgsql-performance@postgresql.org
Cc: tv@fuzzy.cz, andy@squeakycode.net, wohlg@ai.wu.ac.at, heinz@langatium.net, wohlg@ai.wu-wien.ac.at, albert.weichselbraun@wu.ac.at
Subject: Re: Sudden drop in DBb performance
In-Reply-To: <785367bd0412b17bcd89350bcd703de6.squirrel@sq.gransy.com>
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