From: Scott Carey <scott@richrelevance.com>
To: Greg Smith <gsmith@gregsmith.com>
To: Mark Kirkwood <markir@paradise.net.nz>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Raid 10 chunksize
Date: Wed, 25 Mar 2009 09:16:33 -0700
Message-ID: <C5EFA6F1.3B90%scott@richrelevance.com> (raw)
In-Reply-To: <alpine.GSO.2.01.0903250251490.13683@westnet.com>
On 3/25/09 1:07 AM, "Greg Smith" <gsmith@gregsmith.com> wrote:
> On Wed, 25 Mar 2009, Mark Kirkwood wrote:
>
>> I'm thinking that the raid chunksize may well be the issue.
>
> Why? I'm not saying you're wrong, I just don't see why that parameter
> jumped out as a likely cause here.
>
If postgres is random reading or writing at 8k block size, and the raid
array is set with 4k block size, then every 8k random i/o will create TWO
disk seeks since it gets split to two disks. Effectively, iops will be cut
in half.
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To: pgsql-performance@postgresql.org
Cc: scott@richrelevance.com, gsmith@gregsmith.com, markir@paradise.net.nz
Subject: Re: Raid 10 chunksize
In-Reply-To: <C5EFA6F1.3B90%scott@richrelevance.com>
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