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Re: RAID stripe size question

From: "Milen Kulev" <makulev(at)gmx(dot)net>
To: "'Mikael Carneholm'" <Mikael(dot)Carneholm(at)WirelessCar(dot)com>,<pgsql-performance(at)postgresql(dot)org>
Subject: Re: RAID stripe size question
Date: 2006-07-18 20:01:27
Message-ID: 001a01c6aaa4$f45aaee0$0a00a8c0@trivadis.com (view raw or flat)
Thread:
Lists: pgsql-performance
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, 

->>>>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. 
Milen 


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