Re: Query plan looks OK, but slow I/O - settings advice?

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От Jeffrey W. Baker
Тема Re: Query plan looks OK, but slow I/O - settings advice?
Дата
Msg-id 1124434535.3257.7.camel@noodles
обсуждение исходный текст
Ответ на Query plan looks OK, but slow I/O - settings advice?  ("Roger Hand" <RHand@kailea.com>)
Ответы Re: Query plan looks OK, but slow I/O - settings advice?  (Dan Harris <fbsd@drivefaster.net>)
Список pgsql-performance
On Tue, 2005-08-16 at 10:46 -0700, Roger Hand wrote:
> The disks are ext3 with journalling type of ordered, but this was later changed to writeback with no apparent change
inspeed. 
>
> They're on a Dell poweredge 6650 with LSI raid card, setup as follows:
> 4 disks raid 10 for indexes (145GB) - sdc1
> 6 disks raid 10 for data (220GB) - sdd1
> 2 mirrored disks for logs - sdb1
>
> stripe size is 32k
> cache policy: cached io (am told the controller has bbu)
> write policy: write-back
> read policy: readahead

I assume you are using Linux 2.6.  Have you considered booting your
machine with elevator=deadline?  You can also change this at runtime
using sysfs.

These read speeds are not too impressive.  Perhaps this is a slow
controller.  Alternately you might need bigger CPUs.

There's a lot of possibilities, obviously :)  I'd start with the
elevator, since that's easily tested.

-jwb


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