From: "Milen Kulev" <makulev@gmx.net>
To: "'Mikael Carneholm'" <Mikael.Carneholm@WirelessCar.com>,
	<pgsql-performance@postgresql.org>
Subject: Re: RAID stripe size question
Date: Tue, 18 Jul 2006 22:01:27 +0200
Message-ID: <001a01c6aaa4$f45aaee0$0a00a8c0@trivadis.com>
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In-Reply-To: <7F10D26ECFA1FB458B89C5B4B0D72C2B4E4BFA@sesrv12.wirelesscar.com>

According to =
http://www.pcguide.com/ref/hdd/perf/raid/concepts/perfStripe-c.html, it =
seems to be the other way around?
("As stripe size is decreased, files are broken into smaller and smaller =
pieces. This increases the number of drives
that an average file will use to hold all the blocks containing the data =
of that file,=20

->>>>theoretically increasing transfer performance, but decreasing =
positioning performance.")

Mikael,
In OLTP you utterly need  best possible latency.  If you decompose the =
response time if you physical request you will
see positioning performance plays the dominant role in the response time =
(ignore for a moment caches and their effects).

So, if you need really good response times of your SQL queries, choose  =
15 rpm disks(and add as much cache as possible
to magnify the effect ;) )

Best Regards.=20
Milen=20