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From: Greg Smith <gsmith@gregsmith.com>
To: Mathieu Gilardet <mgilardet@alaloop.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: RAM / Disk ratio, any rule?
Date: Wed, 4 Jun 2008 20:32:29 -0400 (EDT)
Message-ID: <Pine.GSO.4.64.0806042027410.3874@westnet.com> (raw)
In-Reply-To: <4846A06F.3090907@alaloop.com>
References: <4846A06F.3090907@alaloop.com>

On Wed, 4 Jun 2008, Mathieu Gilardet wrote:

> Do be more specific, we have an heavy loaded server with SCSI disks 
> (RAID 0 on a SAS controller), making a total of 500GB. Actually, there 
> are 16GB RAM, representing about 2,5% of db size.

That's a reasonable ratio.  Being able to hold somewhere around 1 to 5% of 
the database in RAM seems to common nowadays, and that works OK.  But it's 
impossible to have a hard "rule" here because the working set needed to 
operate the queries and other activities on your server is completely 
dependant on the code you're running, your performance expectations, and 
your expected user load.

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



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