Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id 0BD661337B61 for ; Thu, 7 Oct 2010 20:38:13 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.243]) (amavisd-maia, port 10024) with ESMTP id 95198-05 for ; Thu, 7 Oct 2010 23:38:05 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from polaris.pinpointresearch.com (cerberus.pinpointresearch.com [66.7.238.130]) by mail.postgresql.org (Postfix) with ESMTP id B146C1337B5C for ; Thu, 7 Oct 2010 20:38:05 -0300 (ADT) Received: from betelgeuse.pinpointresearch.com (betelgeuse.pinpointresearch.com [192.168.1.179]) by polaris.pinpointresearch.com (Postfix) with ESMTP id DC2A0E00EC84 for ; Thu, 7 Oct 2010 16:38:04 -0700 (PDT) Message-ID: <4CAE59DC.4060407@pinpointresearch.com> Date: Thu, 07 Oct 2010 16:38:04 -0700 From: Steve Crawford User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.12) Gecko/20100915 Lightning/1.0b1 Thunderbird/3.0.8 MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: BBU Cache vs. spindles Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=-1.91 tagged_above=-10 required=5 tests=BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 X-Spam-Level: X-Archive-Number: 201010/72 X-Sequence-Number: 40491 I'm weighing options for a new server. In addition to PostgreSQL, this machine will handle some modest Samba and Rsync load. I will have enough RAM so the virtually all disk-read activity will be cached. The average PostgreSQL read activity will be modest - a mix of single-record and fairly large (reporting) result-sets. Writes will be modest as well but will come in brief (1-5 second) bursts of individual inserts. The rate of insert requests will hit 100-200/second for those brief bursts. So... Am I likely to be better off putting $$$ toward battery-backup on the RAID or toward adding a second RAID-set and splitting off the WAL traffic? Or something else? Cheers, Steve