Re: Performances issues with SSD volume ?

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-ubuntu-lts-e61d57b70dd4

Have a nice day.

Koray

On Mon, May 18, 2015 at 4:35 PM, Thomas SIMON <tsimon(at)neteven(dot)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(at)neteven(dot)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
>
>
>