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From: Pavel Stehule <pavel.stehule@gmail.com>
To: Hannes Dorbath <light@theendofthetunnel.de>
Cc: pgsql-performance@postgresql.org
Subject: Re: 8.3 synchronous_commit
Date: Mon, 21 Jan 2008 23:11:07 +0100
Message-ID: <162867790801211411j48e2d435lc7bba2b735ccfe45@mail.gmail.com> (raw)
In-Reply-To: <fn34ca$2ff8$1@news.hub.org>
References: <fn34ca$2ff8$1@news.hub.org>

Hello

synchronous_commit = off is well for specific load,

try only one connect pgbench ~ it is analogy for database import or
some administrator's work.

Regards
Pavel Stehule


On 21/01/2008, Hannes Dorbath <light@theendofthetunnel.de> wrote:
> I might completely misunderstand this feature. Shouldn't
> "synchronous_commit = off" improve performance?
>
> Whatever I do, I find "synchronous_commit = off" to degrade performance.
>
> Especially it doesn't like the CFQ I/O scheduler, it's not so bad with
> deadline. Synthetic load like
>
> pgbench -i -s 10 -U pgsql -d bench && pgbench -t 1000 -c 100 -U pgsql -d
> bench
>
> or the same with scale 100.
>
> Maybe it's just my test box.. single SATA-II drive, XFS on top of LVM.
>
> I'll retry without LVM once I have another drive.. I've seen LVM mess
> with other things in the past.
>
>
> --
> Best regards,
> Hannes Dorbath
>
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