Date: Thu, 7 Jun 2007 14:37:48 -0400
From: Andrew Sullivan <ajs@crankycanuck.ca>
To: pgsql-performance@postgresql.org
Subject: Re: Getting Slow
Message-ID: <20070607183748.GL14087@phlogiston.dyndns.org>
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On Thu, Jun 07, 2007 at 01:48:43PM -0400, Joe Lester wrote:
> of a table). Running the same query 4 times in a row would yield  
> dramatically different results... 1.001 seconds, 5 seconds, 22  
> seconds, 0.01 seconds, to complete.

> - When queries are especially slow, the server shows a big spike in  
> read/write activity.

My bet is that you're maxing your disk subsystem somehow.  The
problem with being I/O bound is that it doesn't matter how great you
do on average: if you have too much I/O traffic, it looks like you're
stopped.  Softraid can be expensive -- first thing I'd look at is to
see whether you are in fact hitting 100% of your I/O capacity and, if
so, what your options are for getting more room there.

A

-- 
Andrew Sullivan  | ajs@crankycanuck.ca
"The year's penultimate month" is not in truth a good way of saying
November.
		--H.W. Fowler