Received: from maia.hub.org (maia-3.hub.org [200.46.204.243]) by mail.postgresql.org (Postfix) with ESMTP id DAB19B5DBC4 for ; Mon, 18 Jul 2011 21:40:06 -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 94492-02 for ; Tue, 19 Jul 2011 00:40:00 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from moutng.kundenserver.de (moutng.kundenserver.de [212.227.126.187]) by mail.postgresql.org (Postfix) with ESMTP id 1077CB5D803 for ; Mon, 18 Jul 2011 21:39:59 -0300 (ADT) Received: from [192.168.1.3] (mail.highperformancepostgresql.com [71.179.240.8]) by mrelayeu.kundenserver.de (node=mreu0) with ESMTP (Nemesis) id 0LjfP2-1RKF2k3Qc4-00bmmS; Tue, 19 Jul 2011 02:39:59 +0200 Message-ID: <4E24D25D.6080809@2ndquadrant.com> Date: Mon, 18 Jul 2011 20:39:57 -0400 From: Greg Smith User-Agent: Thunderbird 2.0.0.24 (X11/20100317) MIME-Version: 1.0 To: Andy CC: pgsql-performance@postgresql.org Subject: Re: BBU still needed with SSD? References: <1310953399.25726.YahooMailClassic@web111304.mail.gq1.yahoo.com> In-Reply-To: <1310953399.25726.YahooMailClassic@web111304.mail.gq1.yahoo.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:ylE3ZAzXMYlvcwz9jLUPzZm9poF87RLiclvqKQ7War7 lCNDSGCbtkiKtD6KvoYBkgXwqWtM1RYJFQUpBuZxLllJZ3F2pO uJfCYV1OOwZGMMSW/0OkUDotH865Nd8fL89CYlosWxp8ZdeJ1C Hdx0VgleRlaUAQIrYsXZ651drDNrs6tP1xXLz+Cq03E4Am35JD Kq4f3jy58aeUCQhdD0qvrjQh9l2lHm17ON/Lr0MAqE= 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, RCVD_IN_DNSWL_NONE=-0.0001 X-Spam-Level: X-Archive-Number: 201107/180 X-Sequence-Number: 44392 Andy wrote: > SSD has its own cache. And in certain models such as Intel 320 that cache is backed by capacitors. So in a sense that cache acts as a BBU that's backed by capacitors instead of batteries. > Tests I did on the 320 series says it works fine: http://archives.postgresql.org/message-id/4D9D1FC3.4020207@2ndQuadrant.com And there's a larger discussion of this topic at http://blog.2ndquadrant.com/en/2011/04/intel-ssd-now-off-the-sherr-sh.html that answers this question in a bit more detail. -- Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD