X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id 52F139DC800 for ; Mon, 27 Feb 2006 20:22:25 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 39001-06 for ; Mon, 27 Feb 2006 20:22:28 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from noel.decibel.org (noel.decibel.org [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id 1E9259DC8AA for ; Mon, 27 Feb 2006 20:22:22 -0400 (AST) Received: by noel.decibel.org (Postfix, from userid 1001) id 2B1C75645D; Mon, 27 Feb 2006 18:22:26 -0600 (CST) Received: (hashcash-sendmail, from uid 1001); Mon, 27 Feb 2006 18:22:23 -0600 Date: Mon, 27 Feb 2006 18:22:23 -0600 From: "Jim C. Nasby" To: Tino Wildenhain Cc: Javier Somoza , pgsql-performance@postgresql.org Subject: Re: fsync and battery-backed caches Message-ID: <20060228002223.GW82012@pervasive.com> References: <1141034594.1556.15.camel@pndsoft> <4402D0A9.7080705@wildenhain.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4402D0A9.7080705@wildenhain.de> X-Operating-System: FreeBSD 6.0-RELEASE-p4 amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.11 X-Hashcash: 1:20:060228:tino@wildenhain.de::jfHX0Y3fAICZPhhb:0000000000000000000 000000000000000000000000AGSr X-Hashcash: 1:20:060228:jsomoza@pandasoftware.es::M7gJzIgtYVyEhNeP:0000000000000 0000000000000000000000002qCl X-Hashcash: 1:20:060228:pgsql-performance@postgresql.org::d9YObfzMqiiHPeUN:00000 00000000000000000000000099Cg X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.105 required=5 tests=[AWL=0.105] X-Spam-Score: 0.105 X-Spam-Level: X-Archive-Number: 200602/423 X-Sequence-Number: 17409 On Mon, Feb 27, 2006 at 11:12:57AM +0100, Tino Wildenhain wrote: > Javier Somoza schrieb: > > > > Hi all > > > > Is it secure to disable fsync havin battery-backed disk cache? > > > > Thx > > > No. fsync moves the data from OS memory cache to disk-adaptor > cache which is required to benefit from battery backup. More importantly, in guarantees that data is committed to non-volatile storage in such a way that PostgreSQL can recover from a crash without corruption. If you have a battery-backed controller and turn on write caching you shouldn't see much effect from fsync anyway. -- Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461