Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 30FD16501FF for ; Wed, 13 Aug 2008 10:25:19 -0300 (ADT) Received: from postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 58865-01-8 for ; Wed, 13 Aug 2008 10:24:56 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from smtp107.biz.mail.mud.yahoo.com (smtp107.biz.mail.mud.yahoo.com [68.142.200.255]) by postgresql.org (Postfix) with SMTP id F26D3650340 for ; Wed, 13 Aug 2008 10:24:29 -0300 (ADT) Received: (qmail 83697 invoked from network); 13 Aug 2008 13:24:28 -0000 Received: from unknown (HELO ?192.168.5.105?) (ramayer@forensiclogic.com@75.37.20.87 with plain) by smtp107.biz.mail.mud.yahoo.com with SMTP; 13 Aug 2008 13:24:27 -0000 X-YMail-OSG: 40e9zesVM1kz2cR6cJ43F4qgyn1YWlZNImivfhPtBrPHY1X69kEG9KVkI6ge6Ngq4TBakJrbaPi.UBZ4nmyGQ9aePHPskhuIxSuWlwZgpJEJUrGg58Qp8U6fga2Hsja3a5HZiD4iwFvFQ6LPJ5HzPHWA X-Yahoo-Newman-Property: ymail-3 Message-ID: <48A2E08D.6000103@cheapcomplexdevices.com> Date: Wed, 13 Aug 2008 06:24:29 -0700 From: Ron Mayer User-Agent: Mozilla-Thunderbird 2.0.0.16 (X11/20080724) MIME-Version: 1.0 To: Scott Marlowe CC: Ron Mayer , Scott Carey , Greg Smith , Henrik , pgsql-performance@postgresql.org Subject: Re: Filesystem benchmarking for pg 8.3.3 server References: <32A7A76B-16CA-4CDB-AD43-973AD6A3FC7B@mac.se> <48A2050D.4050803@cheapcomplexdevices.com> <48A262F0.9080203@cheapcomplexdevices.com> In-Reply-To: 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=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200808/149 X-Sequence-Number: 31030 Scott Marlowe wrote: > On Tue, Aug 12, 2008 at 10:28 PM, Ron Mayer ...wrote: >> Scott Marlowe wrote: >>> I can attest to the 2.4 kernel ... >> ...SCSI...AFAICT the write barrier support... > > Tested both by pulling the power plug. The SCSI was pulled 10 times > while running 600 or so concurrent pgbench threads, and so was the > IDE. The SCSI came up clean every single time, the IDE came up > corrupted every single time. Interesting. With a pre-write-barrier 2.4 kernel I'd expect corruption in both. Perhaps all caches were disabled in the SCSI drives? > I find it hard to believe there was no difference in write barrier > behaviour with those two setups. Skimming lkml it seems write barriers for SCSI were behind (in terms of implementation) those for ATA http://lkml.org/lkml/2005/1/27/94 "Jan 2005 ... scsi/sata write barrier support ... For the longest time, only the old PATA drivers supported barrier writes with journalled file systems. This patch adds support for the same type of cache flushing barriers that PATA uses for SCSI"