Received: from maia.hub.org (maia-2.hub.org [200.46.204.251]) by mail.postgresql.org (Postfix) with ESMTP id 7F30FB5DBD9 for ; Thu, 18 Aug 2011 02:36:18 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia, port 10024) with ESMTP id 65022-04 for ; Thu, 18 Aug 2011 05:36:12 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from mail-pz0-f42.google.com (mail-pz0-f42.google.com [209.85.210.42]) by mail.postgresql.org (Postfix) with ESMTP id 09330B5D80A for ; Thu, 18 Aug 2011 02:36:11 -0300 (ADT) Received: by pzk37 with SMTP id 37so3984623pzk.15 for ; Wed, 17 Aug 2011 22:36:11 -0700 (PDT) Received: by 10.142.118.25 with SMTP id q25mr177195wfc.274.1313645771350; Wed, 17 Aug 2011 22:36:11 -0700 (PDT) Received: from [192.168.3.155] (office1.postnewspapers.com.au [150.101.171.128]) by mx.google.com with ESMTPS id e6sm1188602pbm.87.2011.08.17.22.36.08 (version=SSLv3 cipher=OTHER); Wed, 17 Aug 2011 22:36:10 -0700 (PDT) Message-ID: <4E4CA4BC.9050908@ringerc.id.au> Date: Thu, 18 Aug 2011 13:35:56 +0800 From: Craig Ringer User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:5.0) Gecko/20110624 Thunderbird/5.0 MIME-Version: 1.0 To: Ogden CC: pgsql-performance@postgresql.org, Greg Smith Subject: Re: Raid 5 vs Raid 10 Benchmarks Using bonnie++ References: <959BD2FA-0312-458B-BD5F-ED358D2C47ED@darkstatic.com> <75A85649-2B95-43D5-8404-4776D2E580EC@darkstatic.com> <4E4C2FB4.4010409@2ndQuadrant.com> <207E881B-73CD-4C31-A863-2C238838C41F@darkstatic.com> In-Reply-To: <207E881B-73CD-4C31-A863-2C238838C41F@darkstatic.com> 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=-1.9 tagged_above=-10 required=5 tests=BAYES_00=-1.9 X-Spam-Level: X-Archive-Number: 201108/218 X-Sequence-Number: 44665 On 18/08/2011 11:48 AM, Ogden wrote: > Isn't this very dangerous? I have the Dell PERC H700 card - I see that it has 512Mb Cache. Is this the same thing and good enough to switch to nobarrier? Just worried if a sudden power shut down, then data can be lost on this option. > > Yeah, I'm confused by that too. Shouldn't a write barrier flush data to persistent storage - in this case, the RAID card's battery backed cache? Why would it force a RAID controller cache flush to disk, too? -- Craig Ringer