Re: Getting Slow - Mailing list pgsql-performance

From Andrew Sullivan
Subject Re: Getting Slow
Date
Msg-id 20070607183748.GL14087@phlogiston.dyndns.org
Whole thread Raw
In response to Getting Slow  (Joe Lester <joe_lester@sweetwater.com>)
List pgsql-performance
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

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