Received: from maia.hub.org (maia-5.hub.org [200.46.204.29]) by mail.postgresql.org (Postfix) with ESMTP id 9EBC01337A5D for ; Wed, 6 Apr 2011 22:32:09 -0300 (ADT) Received: from mail.postgresql.org ([200.46.204.86]) by maia.hub.org (mx1.hub.org [200.46.204.29]) (amavisd-maia, port 10024) with ESMTP id 56799-07 for ; Thu, 7 Apr 2011 01:32:00 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from moutng.kundenserver.de (moutng.kundenserver.de [212.227.126.186]) by mail.postgresql.org (Postfix) with ESMTP id C4A911337B2F for ; Wed, 6 Apr 2011 22:31:58 -0300 (ADT) Received: from [192.168.1.6] (mail.highperformancepostgresql.com [71.179.240.8]) by mrelayeu.kundenserver.de (node=mreu1) with ESMTP (Nemesis) id 0LrXBZ-1PvWBE3oPl-013Mzl; Thu, 07 Apr 2011 03:31:58 +0200 Message-ID: <4D9D142B.3030809@2ndQuadrant.com> Date: Wed, 06 Apr 2011 21:32:27 -0400 From: Greg Smith User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20110307 Icedove/3.0.11 MIME-Version: 1.0 To: pgsql-performance@postgresql.org Subject: Re: Intel SSDs that may not suck References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:Zd5j7baN6rahBydlpeQvxloZQjYVPmV+v2UFQBraq6n 0Oe5mZ+NRRTVjqjmIMZgOw2CSHb1IEOwb3oni64N66YLETPLre rAVqUOXR9SRjFLR19RjTgKkdyZv5xhiUpRPb6LFF0BFnAzA7pn dW/3/aMBakKkIUlyGvlHNCOL0FIN0W+0Idb6jAD89vO0d0mJkg jyilU8FtFbC5Fx0FrNAfi49ILcUdW+PpuvFyst5FgM= 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: 201104/63 X-Sequence-Number: 43125 On 04/06/2011 08:22 PM, Scott Carey wrote: > Simple power failure tests demonstrate that you lose data with these > drives unless you disable the cache. Disabling the cache roughly drops > write performance by a factor of 3 to 4 on G1 drives and significantly > hurts wear-leveling and longevity (I haven't tried G2's). > Yup. I have a customer running a busy system with Intel X25-Es, and another with X25-Ms, and every time there is a power failure at either place their database gets corrupted. That those drives are worthless for a reliable database setup has been clear for two years now: http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/ and sometimes I even hear reports about those drives getting corrupted even when the write cache is turned off. If you aggressively replicate the data to another location on a different power grid, you can survive with Intel's older drives. But odds are you're going to lose at least some transactions no matter what you do, and the risk of "database won't start" levels of corruption is always lingering. The fact that Intel is making so much noise over the improved write integrity features on the new drives gives you an idea how much these problems have hurt their reputation in the enterprise storage space. -- Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books