X-Original-To: pgsql-performance-postgresql.org@postgresql.org Received: from localhost (mx1.hub.org [200.46.208.251]) by postgresql.org (Postfix) with ESMTP id D4DEA9FA5BA for ; Thu, 15 Jun 2006 12:54:32 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.208.251]) (amavisd-new, port 10024) with ESMTP id 15314-02 for ; Thu, 15 Jun 2006 12:54:23 -0300 (ADT) 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 1E8DB9F9CAA for ; Thu, 15 Jun 2006 12:54:22 -0300 (ADT) Received: by noel.decibel.org (Postfix, from userid 1001) id 9A2A256475; Thu, 15 Jun 2006 10:54:21 -0500 (CDT) Received: (hashcash-sendmail, from uid 1001); Thu, 15 Jun 2006 10:54:20 -0500 Date: Thu, 15 Jun 2006 10:54:20 -0500 From: "Jim C. Nasby" To: "Jonah H. Harris" Cc: Greg Stark , Mark Lewis , Dan Gorman , pgsql-performance@postgresql.org Subject: Re: Postgres fsync off (not needed) with NetApp Message-ID: <20060615155420.GK34196@pervasive.com> References: <9A377C54-361D-4F01-BF7A-7632FBA3453C@hi5.com> <1150322085.31200.39.camel@archimedes> <873be7ay8u.fsf@stark.xeocode.com> <36e682920606142214i6a6532f3k1a895a784f7b16dc@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <36e682920606142214i6a6532f3k1a895a784f7b16dc@mail.gmail.com> 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: 1:20:060615:jonah.harris@gmail.com::wtcCzDPceckKqhjb:000000000000000 00000000000000000000000041Kv X-Hashcash: 1:20:060615:gsstark@mit.edu::2n8kW7z1OmRymRJV:001NWB X-Hashcash: 1:20:060615:mark.lewis@mir3.com::THeZxH9LHu6zJ/+2:000000000000000000 00000000000000000000000042I1 X-Hashcash: 1:20:060615:dgorman@hi5.com::x8zjZvWoXQ27GChe:005xA5 X-Hashcash: 1:20:060615:pgsql-performance@postgresql.org::QouyWI9dyU16Fyu6:00000 00000000000000000000000002yG X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200606/308 X-Sequence-Number: 19665 On Thu, Jun 15, 2006 at 01:14:26AM -0400, Jonah H. Harris wrote: > On 14 Jun 2006 23:33:53 -0400, Greg Stark wrote: > >In fact the benefit of the NVRAM is precisely that it makes sure you > >*don't* > >have any reason to turn fsync off. It should make the fsync essentially > >free. > > Having run PostgreSQL on a NetApp with input from NetApp, this is > correct. fsync should be turned on, but you will not incur the *real* > direct-to-disk cost of the sync, it will be direct-to-NVRAM. Just so there's no confusion... this applies to any caching RAID controller as well. You just need to ensure that the cache in the controller absolutely will not be lost in the event of a power failure or what-have-you. On most controllers this is accomplished with a simple battery backup; I don't know if the higher-end stuff takes further steps (such as flashing the cache contents to flash memory on a power failure). -- 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