X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id BFAA4D8E7D for ; Wed, 14 Sep 2005 17:02:10 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 32846-02 for ; Wed, 14 Sep 2005 20:02:02 +0000 (GMT) Received: from mx1.surnet.cl (mx1.surnet.cl [216.155.73.180]) by svr1.postgresql.org (Postfix) with ESMTP id DB861D81F7 for ; Wed, 14 Sep 2005 17:02:01 -0300 (ADT) Received: from unknown (HELO cluster.surnet.cl) ([216.155.73.165]) by mx1.surnet.cl with ESMTP; 14 Sep 2005 16:02:57 -0400 X-IronPort-AV: i="3.97,110,1125892800"; d="scan'208"; a="8299397:sNHT30388438" Received: from alvh.no-ip.org (216.155.86.232) by cluster.surnet.cl (7.0.043) (authenticated as alvherre@surnet.cl) id 4327E85F00012952; Wed, 14 Sep 2005 16:02:03 -0400 Received: by alvh.no-ip.org (Postfix, from userid 1000) id B0B91C2DC1A; Wed, 14 Sep 2005 16:03:24 -0400 (CLT) Date: Wed, 14 Sep 2005 16:03:24 -0400 From: Alvaro Herrera To: "Jeffrey W. Baker" Cc: Peter Darley , Pgsql-Performance Subject: Re: Battery Backed Cache for RAID Message-ID: <20050914200324.GB26714@surnet.cl> Mail-Followup-To: "Jeffrey W. Baker" , Peter Darley , Pgsql-Performance References: <1126722523.27650.6.camel@toonses.gghcwest.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1126722523.27650.6.camel@toonses.gghcwest.com> User-Agent: Mutt/1.5.10i X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=2.65 required=5 tests=[AWL=-0.697, DNS_FROM_RFC_ABUSE=0.374, DNS_FROM_RFC_POST=1.376, RCVD_IN_SORBS_MISC=1.597] X-Spam-Level: ** X-Archive-Number: 200509/192 X-Sequence-Number: 14500 On Wed, Sep 14, 2005 at 11:28:43AM -0700, Jeffrey W. Baker wrote: > On Wed, 2005-09-14 at 11:25 -0700, Peter Darley wrote: > > I'm getting a new server for our database, and I have a quick question > > about RAID controllers with a battery backed cache. I understand that the > > cache will allow the cache to be written out if the power fails to the box, > > which allows it to report a write as committed safely when it's not actually > > committed. > > Actually the cache will just hold its contents while the power is out. > When the power is restored, the RAID controller will complete the writes > to disk. If the battery does not last through the outage, the data is > lost. Just curious: how long are the batteries supposed to last? -- Alvaro Herrera -- Valdivia, Chile Architect, www.EnterpriseDB.com Hi! I'm a .signature virus! cp me into your .signature file to help me spread!