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From: Greg Smith <gsmith@gregsmith.com>
To: pgsql-performance@postgresql.org
Subject: Re: Volunteer to build a configuration tool
Date: Sat, 23 Jun 2007 15:28:17 -0400 (EDT)
Message-ID: <Pine.GSO.4.64.0706231522460.1349@westnet.com> (raw)
In-Reply-To: <A3AC4FA47DC0B1458C3E5396E685E63302395E74@SAB-DC1.sab.uiuc.edu>
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	<A3AC4FA47DC0B1458C3E5396E685E63302395E6C@SAB-DC1.sab.uiuc.edu>
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	<A3AC4FA47DC0B1458C3E5396E685E63302395E74@SAB-DC1.sab.uiuc.edu>

On Thu, 21 Jun 2007, Campbell, Lance wrote:

> I have a PostgreSQL database that runs on a dedicated server.  The
> server has 24Gig of memory.  What would be the max size I would ever
> want to set the shared_buffers to if I where to relying on the OS for
> disk caching approach?  It seems that no matter how big your dedicated
> server is there would be a top limit to the size of shared_buffers.

It's impossible to say exactly what would work optimally in this sort of 
situation.  The normal range is 25-50% of total memory, but there's no 
hard reason for that balance; for all we know your apps might work best 
with 20GB in shared_buffers and only a relatively small 4GB left over for 
the rest of the OS to use.  Push it way up and and see what you get.

This is part of why the idea of an "advanced" mode for this tool is 
suspect.  Advanced tuning usually requires benchmarking with as close to 
real application data as you can get in order to make good forward 
progress.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD



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