From: Greg Smith <greg@2ndquadrant.com>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: pgsql-performance@postgresql.org, Claire Chang <yenhsiac@yahoo.com>
Subject: Re: Postgres 8.4 memory related parameters
Date: Mon, 08 Aug 2011 23:59:08 -0400
Message-ID: <4E40B08C.6010309@2ndquadrant.com> (raw)
In-Reply-To: <4E3ABCFB020000250003FAF4@gw.wicourts.gov>
References: <1312489633.71838.YahooMailClassic@web31912.mail.mud.yahoo.com>
<4E3ABCFB020000250003FAF4@gw.wicourts.gov>
Kevin Grittner wrote:
> Claire Chang <yenhsiac@yahoo.com> wrote:
>
>> shared_buffers = 32GB
>>
>
> I seem to remember seeing some benchmarks showing that performance
> falls off after 10GB or 20GB on that setting.
>
Not even quite that high. I've never heard of a setting over 10GB being
anything other than worse than a smaller setting, and that was on
Solaris. At this point I never consider a value over 8GB, and even that
needs to be carefully matched against how heavy the writes on the server
are. You just can't set shared_buffers to a huge value in PostgreSQL
yet, and "huge" means ">8GB" right now.
Note that the problems you can run into with too much buffer cache are
much worse with a low setting for checkpoint_segments...and this
configuration doesn't change it at all from the tiny default. That
should go to at least 64 on a server this size.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
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To: pgsql-performance@postgresql.org
Cc: greg@2ndquadrant.com, Kevin.Grittner@wicourts.gov, yenhsiac@yahoo.com
Subject: Re: Postgres 8.4 memory related parameters
In-Reply-To: <4E40B08C.6010309@2ndquadrant.com>
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