From: Martin Nickel <martin@portant.com>
Subject: Re: shared buffers
Date: Sun, 04 Sep 2005 21:56:01 -0500
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To: pgsql-performance@postgresql.org

Chris,
Would you say that 30000 pages is a good maximum for a Postgres install?
We're running 8.0.3 on 64-bit SUSE on a dual Opteron box with 4G and have
shared_buffers set at 120000.  I've moved it up and down (it was 160000
when I got here) without any measurable performance difference.

The reason I ask is because I occasionally see large-ish queries take
forever (like cancel-after-12-hours forever) and wondered if this could
result from shared_buffers being too large.

Thanks for your (and anyone else's) help!
Martin Nickel

On Tue, 30 Aug 2005 10:08:21 +0800, Christopher Kings-Lynne wrote:

>> I forgot to say that it´s a 12GB database...
> 
> That's actually not that large.
> 
>> Ok, I´ll set shared buffers to 30.000 pages but even so "meminfo" and 
>> "top" shouldn´t show some shared pages?
> 
> Yeah. The reason for not setting buffers so high is because PostgreSQL 
> cannot efficiently manage huge shared buffers, so you're better off 
> giving the RAM to Linux's disk cache.
> 
> Chris
> 
> 
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