Received: from localhost (unknown [200.46.204.183]) by developer.postgresql.org (Postfix) with ESMTP id E50A82E0079 for ; Wed, 4 Jun 2008 11:08:50 -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 81143-06 for ; Wed, 4 Jun 2008 11:08:30 -0300 (ADT) X-Greylist: delayed 00:06:04.873729 by SQLgrey-1.7.6 Received: from zimbra-ne01.network-studio.com (zimbra-ne01.network-studio.com [62.93.225.49]) by developer.postgresql.org (Postfix) with ESMTP id 6B3772E0041 for ; Wed, 4 Jun 2008 11:08:36 -0300 (ADT) Received: from localhost (localhost.localdomain [127.0.0.1]) by zimbra-ne01.network-studio.com (Postfix) with ESMTP id 88B8E861EA3 for ; Wed, 4 Jun 2008 16:02:27 +0200 (CEST) X-Virus-Scanned: amavisd-new at Received: from zimbra-ne01.network-studio.com ([127.0.0.1]) by localhost (zimbra-ne01.network-studio.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Pet9yNYM3MZv for ; Wed, 4 Jun 2008 16:02:23 +0200 (CEST) Received: from [10.2.1.59] (27.71.64-86.rev.gaoland.net [86.64.71.27]) by zimbra-ne01.network-studio.com (Postfix) with ESMTP id ADC62861CDE for ; Wed, 4 Jun 2008 16:02:23 +0200 (CEST) Message-ID: <4846A06F.3090907@alaloop.com> Date: Wed, 04 Jun 2008 16:02:23 +0200 From: Mathieu Gilardet User-Agent: Mozilla-Thunderbird 2.0.0.14 (X11/20080509) MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: RAM / Disk ratio, any rule? Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200806/18 X-Sequence-Number: 30368 hello, I am wondering if actually, does exists any rule to determine the amount of RAM, according to the hardware disk size (in prevision to use all or nearly available space), when designing a server? Of course fsm settings implies that when db size grows, more memory will be in use for tracking free space. Same thing applies from RAM cache effectiveness: the bigger db size is, the more RAM is needed. 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. any experiences to share? in advance, thank you. Mathieu