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Re: Ideal disk setup for Postgresql 7.4?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Steve Poe <spoe(at)sfnet(dot)cc>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Ideal disk setup for Postgresql 7.4?
Date: 2005-01-26 21:39:49
Message-ID: 20267.1106775589@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Steve Poe <spoe(at)sfnet(dot)cc> writes:
>> Well, it's less bad with 7 disks than it is with 3, certainly.   However,there 
>> is an obvious and quick gain to be had by splitting off the WAL logs onto 
>> their own disk resource ... up to 14%+ performance in some applications.
>> 
> Pardon my ignorance, but the WAL logs are comprised of pg_xlog and 
> pg_clog? Their own disk resource, but not within the same channel of 
> disks the database is on, right?

Just pg_xlog.  Ideally you don't want any other traffic on the physical
disk pg_xlog is on --- the idea is that the write heads need to stay
over the current xlog file.  I don't think it hurts too much to share a
controller channel though.

			regards, tom lane

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