Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id 1AD4E2E005B for ; Wed, 4 Jun 2008 21:52:14 -0300 (ADT) Received: from developer.postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 32906-03-2 for ; Wed, 4 Jun 2008 21:51:54 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from westnet.com (westnet.com [216.187.52.2]) by developer.postgresql.org (Postfix) with ESMTP id 552FC2E019C for ; Wed, 4 Jun 2008 21:32:32 -0300 (ADT) Received: from westnet.com (localhost [127.0.0.1]) by westnet.com (8.14.0/8.14.0) with ESMTP id m550WU0k006180; Wed, 4 Jun 2008 20:32:30 -0400 (EDT) Received: from localhost (gsmith@localhost) by westnet.com (8.14.0/8.13.2/Submit) with ESMTP id m550WT3F006176; Wed, 4 Jun 2008 20:32:29 -0400 (EDT) X-Authentication-Warning: westnet.com: gsmith owned process doing -bs Date: Wed, 4 Jun 2008 20:32:29 -0400 (EDT) From: Greg Smith X-X-Sender: gsmith@westnet.com To: Mathieu Gilardet cc: pgsql-performance@postgresql.org Subject: Re: RAM / Disk ratio, any rule? In-Reply-To: <4846A06F.3090907@alaloop.com> Message-ID: References: <4846A06F.3090907@alaloop.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200806/32 X-Sequence-Number: 30382 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