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Date: Thu, 29 Apr 2010 12:35:01 -0700
Message-ID: <y2mf2fd819a1004291235wce7d12e8y6f4ae5feaf77d7f8@mail.gmail.com>
Subject: Re: more 10K disks or less 15K disks
From: Anj Adu <fotographs@gmail.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Greg Smith <greg@2ndquadrant.com>, pgsql-admin@postgresql.org
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With the increase in the number of disks that we can afford to have in
1 box..we will definitely plan on having WAL on dedicated disks.
Previously..we were stuck with the chassis limitation of 6 disks per
box.

On Thu, Apr 29, 2010 at 12:25 PM, Scott Marlowe <scott.marlowe@gmail.com> w=
rote:
> On Thu, Apr 29, 2010 at 11:26 AM, Anj Adu <fotographs@gmail.com> wrote:
>> All the disks are usually laid out in a single RAID 10 stripe . There
>> are no dedicated disks for the OS/WAL as storage is a premium
>
> You should at least investigate the performance difference of having a
> separate volume for WAL files on your system. =A0 =A0Since WAL files are
> mostly sequential, and db access is generally random, the WAL files
> can run really quickly on a volume that does nothing else but handle
> WAL writes sequentially. =A0Given the volume you're handling, I would
> expect that storage is not any more important than performance.
>
> The fact that you're asking whether to go with 12 or 24 600G disks
> shows that you're willing to give up a little storage for performance.
> =A0I would bet that the 24 10k disks with one pair dedicated for OS /
> pg_xlog would be noticeably faster than any single large volume config
> you'd care to test, especially for lots of active connections.
>