From: Thomas SIMON <tsimon@neteven.com>
To: pgsql-admin@postgresql.org <pgsql-admin@postgresql.org>
Subject: Re: Performances issues with SSD volume ?
Date: Mon, 18 May 2015 16:17:38 +0200
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Wow, thanks a lot for advice Koray!
This is a huge difference indeed !
I will start with upgrading my kernel asap :)
Thomas
Le 18/05/2015 15:51, Koray Eyidoğan a écrit :
> Hi Thomas,
>
> 3.2 kernel may be #1 cause of your I/O load problem:
>
> http://www.databasesoup.com/2014/09/why-you-need-to-avoid-linux-kernel-32.html
> https://medium.com/postgresql-talk/benchmarking-postgresql-with-different-linux-kernel-versions-on-u...
>
> Have a nice day.
>
> Koray
>
>
> On Mon, May 18, 2015 at 4:35 PM, Thomas SIMON <tsimon@neteven.com
> <mailto:tsimon@neteven.com>> wrote:
>
> Hi matheus,
> thanks for reply.
>
> Kernel is slightly different ; with a 3.10.23-xxxx-std-ipv6-64
> kernel (OVH kernel) on HDD server, and 3.2.65-1+deb7u1 kernel on
> SSD server.
> I'm using debian wheezy on both servers.
>
> I didn't changed the 2 parameters you talk about.
>
> Thanks,
>
> Thomas
>
> Le 18/05/2015 15:13, Matheus de Oliveira a écrit :
>>
>> On Mon, May 18, 2015 at 10:05 AM, Thomas SIMON
>> <tsimon@neteven.com <mailto:tsimon@neteven.com>> wrote:
>>
>> After the change, I had the following behavior, and I don't
>> understand why : everything seems to work fine (load is ~6/7,
>> when it was previously ~25/30 on the HDD server), so the SSD
>> server is faster than the HDD one, and my apps run faster
>> too, but after some time (can be 5 minutes or 2 hours), the
>> load average increases suddently (can reach 150 !) and does
>> not decrease, so postgres and my application are almost
>> unusable. (even small requests are in statement timeout)
>>
>>
>> Before we go mad, what is the OS/kernel/distro that you are
>> using? Did it change from the previous one?
>>
>> If Linux, have you disabled transparent_huge_pages and
>> zone_reclaim_mode (two known problematic Linux features)?
>>
>> Best regards,
>> --
>> Matheus de Oliveira
>> Analista de Banco de Dados
>> Dextra Sistemas - MPS.Br nível F!
>> www.dextra.com.br/postgres <http://www.dextra.com.br/postgres/;
>>
>
>
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Subject: Re: Performances issues with SSD volume ?
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