Date: Mon, 18 May 2015 14:29:01 +0000 (UTC)
From: Glyn Astill <glynastill@yahoo.co.uk>
Reply-To: Glyn Astill <glynastill@yahoo.co.uk>
To: =?UTF-8?Q?Koray_Eyido=C4=9Fan?= <korayey@gmail.com>,
 Thomas SIMON <tsimon@neteven.com>
Cc: "pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>
Message-ID: <1770498187.1993351.1431959341984.JavaMail.yahoo@mail.yahoo.com>
In-Reply-To: 
 <CAOrEZuhNQ1qpqMbHDa=iMxtcceQ12GN+T8DijvRghYr2SHq0WA@mail.gmail.com>
References: 
 <CAOrEZuhNQ1qpqMbHDa=iMxtcceQ12GN+T8DijvRghYr2SHq0WA@mail.gmail.com>
Subject: Re: Performances issues with SSD volume ?
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> From: Koray Eyido=C4=9Fan <korayey@gmail.com>
>To: Thomas SIMON <tsimon@neteven.com>=20
>Cc: pgsql-admin@postgresql.org=20
>Sent: Monday, 18 May 2015, 14:51
>Subject: Re: [ADMIN] Performances issues with SSD volume ?
>=20
>
>
>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


Likely 3.2 kernel isn't helping, but I think we need much more information =
before jumping to conclusions.

You say you're IO bound, so some output from sar / iostat / dstat and pg_st=
at_activity etc before and during the issue would be of use.

Also:
    System memory size

    SSD Model numbers and how many
    Raid controller
    Partition allignments and stripe sizes
    Kernel options
    Filesystem used and mount options
    IO Scheduler
    Postgresql version and configuration
    Connection pool sizing

=20
Perhaps you could thow us the output of some of these:

    fdisk -l
    cat /etc/mtab
    cat /sys/block/<ssd device>/queue/scheduler
    sysctl kernel | grep sched
    sysctl vm
    select * from pg_stat_activity
    select name, setting from pg_settings
    lspci | grep -E 'RAID|SCSI|IDE|SATA'


--=20
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