From: Robert Schnabel <schnabelr@missouri.edu>
To: Scott Carey <scott@richrelevance.com>
Cc: Alan Hodgson <ahodgson@simkin.ca>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: How to best use 32 15k.7 300GB drives?
Date: Fri, 28 Jan 2011 15:33:28 -0600
Message-ID: <4D433628.6010209@missouri.edu> (raw)
In-Reply-To: <C9683F12.1E3D5%scott@richrelevance.com>
References: <C9683F12.1E3D5%scott@richrelevance.com>
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On 1/28/2011 11:44 AM, Scott Carey wrote:
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<div>On 1/27/11 4:11 PM, "Alan Hodgson" <<a
moz-do-not-send="true" href="mailto:ahodgson@simkin.ca">ahodgson@simkin.ca</a>>
wrote:</div>
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<p style="margin: 0px; text-indent: 0px;">On January 27,
2011, Robert Schnabel <<a moz-do-not-send="true"
href="mailto:schnabelr@missouri.edu">schnabelr@missouri.edu</a>>
wrote:</p>
<p style="margin: 0px; text-indent: 0px;">> So my
questions are 1) am I'm crazy for doing this, 2) would
you change</p>
<p style="margin: 0px; text-indent: 0px;">> anything
and 3) is it acceptable to put the xlog & wal (and
perhaps tmp</p>
<p style="margin: 0px; text-indent: 0px;">> filespace)
on a different controller than everything else? Please
keep</p>
<p style="margin: 0px; text-indent: 0px;">> in mind I'm
a geneticist who happens to know a little bit about</p>
<p style="margin: 0px; text-indent: 0px;">>
bioinformatics and not the reverse. :-)</p>
<p style="margin: 0px; text-indent: 0px;">> </p>
<p style="margin: 0px; text-indent: 0px;">Putting the WAL
on a second controller does help, if you're write-heavy.</p>
<p style="margin: 0px; text-indent: 0px;">I tried
separating indexes and data once on one server and
didn't really notice that it helped much. Managing the
space was problematic. I would suggest putting those
together on a single RAID-10 of all the 300GB drives
(minus a spare). It will probably outperform separate
arrays most of the time, and be much easier to manage.</p>
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<div>If you go this route, I suggest two equally sized RAID 10's
on different controllers fir index + data, with software raid-0
on top of that. RAID 10 will max out a controller after 6 to 10
drives, usually. Using the OS RAID 0 to aggregate the
throughput of two controllers works great.</div>
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<div>WAL only has to be a little bit faster than your network in
most cases. I've never seen it be a bottleneck on large bulk
loads if it is on its own controller with 120MB/sec write
throughput. I suppose a bulk load from COPY might stress it a
bit more, but CPU ends up the bottleneck in postgres once you
have I/O hardware this capable.</div>
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Do you mean 14 drives in one box as RAID10's on one controller, then
14 drives in the other box on a second controller, then software
RAID0 each of the two RAID10's together essentially as a single 4 TB
array? Would you still recommend doing this with Windows?<br>
Bob<br>
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To: pgsql-performance@postgresql.org
Cc: schnabelr@missouri.edu, scott@richrelevance.com, ahodgson@simkin.ca
Subject: Re: How to best use 32 15k.7 300GB drives?
In-Reply-To: <4D433628.6010209@missouri.edu>
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