Received: from makus.postgresql.org (makus.postgresql.org [98.129.198.125]) by mail.postgresql.org (Postfix) with ESMTP id C703F5EC6B9 for ; Mon, 16 Jan 2012 18:36:10 -0400 (AST) Received: from moutng.kundenserver.de ([212.227.17.8]) by makus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1Rmv9r-0004T6-5q for pgsql-performance@postgresql.org; Mon, 16 Jan 2012 22:36:11 +0000 Received: from [192.168.1.6] (mail.highperformancepostgresql.com [71.179.240.8]) by mrelayeu.kundenserver.de (node=mreu1) with ESMTP (Nemesis) id 0M9cEd-1Rxc8b0NaR-00CQQl; Mon, 16 Jan 2012 23:35:54 +0100 Message-ID: <4F14A649.5060501@2ndQuadrant.com> Date: Mon, 16 Jan 2012 17:35:53 -0500 From: Greg Smith User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111120 Icedove/3.1.16 MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: wal_level=archive gives better performance than minimal - why? References: <4F0F6A02.3000403@fuzzy.cz> In-Reply-To: <4F0F6A02.3000403@fuzzy.cz> Content-Type: text/plain; charset=ISO-8859-2; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:l1M1bkZLNq9vgOAGXiWTPilEU5g4BExXO+gomnoBSyY fPjgLlwyzsmD9XxFoe2klM47P2+jb6qhfGRhWKtjE8uW1Re7H5 iBFPxk12xIJnOQFOi7DevgZ/7h9CvWnhZszt1oeHqbYHeNtBSk 6s1raZMl/DRnFa98C+rKdEzRJ/BnYahrWM0PwkZ7GTJpV/tstp IJlR4fcBRZxwEBFyryOAo0uuY393MysGHl73rkejHAxlJD+k0j BIPDBh391gqbEYhXtF/UkChsqtBa2X/S1hKFN/zy8xsCe2Jwlz 6mP9Uzl3wl699CpN7CwI6p3Rv8XTIwW+zJw0qFehvAKFeMtux5 4sLC4z74ex8Qc/l4uwtM= X-Pg-Spam-Score: 0.1 (/) X-Archive-Number: 201201/48 X-Sequence-Number: 46061 On 01/12/2012 06:17 PM, Tomas Vondra wrote: > I've run a series fo pgbench benchmarks with the aim to see the effect > of moving the WAL logs to a separate drive, and one thing that really > surprised me is that the archive log level seems to give much better > performance than minimal log level. How repeatable is this? If you always run minimal first and then archive, that might be the actual cause of the difference. In this situation I would normally run this 12 times, with this sort of pattern: minimal minimal minimal archive archive archive minimal minimal minimal archive archive archive To make sure the difference wasn't some variation on "gets slower after each run". pgbench suffers a lot from problems in that class. -- Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com