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 5762E9DC9E8 for ; Tue, 20 Dec 2005 15:52:29 -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 54400-01 for ; Tue, 20 Dec 2005 15:52:24 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from noel.decibel.org (unknown [67.100.216.10]) by postgresql.org (Postfix) with ESMTP id 6D2B19DC81C for ; Tue, 20 Dec 2005 15:52:21 -0400 (AST) Received: by noel.decibel.org (Postfix, from userid 1001) id 9736939830; Tue, 20 Dec 2005 13:52:20 -0600 (CST) Date: Tue, 20 Dec 2005 13:52:20 -0600 From: "Jim C. Nasby" To: David Lang Cc: Anjan Dave , pgsql-performance@postgresql.org Subject: Re: separate drives for WAL or pgdata files Message-ID: <20051220195220.GK28771@pervasive.com> References: <4BAFBB6B9CC46F41B2AD7D9F4BBAF785098F10@vt-pe2550-001.vantage.vantage.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: FreeBSD 6.0-RELEASE amd64 X-Distributed: Join the Effort! http://www.distributed.net User-Agent: Mutt/1.5.11 X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.041 required=5 tests=[AWL=0.041] X-Spam-Score: 0.041 X-Spam-Level: X-Archive-Number: 200512/510 X-Sequence-Number: 16331 On Mon, Dec 19, 2005 at 07:20:56PM -0800, David Lang wrote: > for persistant storage you can replicate from your ram-based system to a > disk-based system, and as long as your replication messages hit disk > quickly you can allow the disk-based version to lag behind in it's updates > during your peak periods (as long as it is able to catch up with the > writes overnight), and as the disk-based version won't have to do the > seeks for the reads it will be considerably faster then if it was doing > all the work (especially if you have good, large battery-backed disk > caches to go with those drives to consolodate the writes) Huh? Unless you're doing a hell of a lot of writing just run a normal instance and make sure you have enough bandwidth to the drives with pg_xlog on it. Make sure those drives are using a battery-backed raid controller too. You'll also need to tune things to make sure that checkpoints never have much (if any) work to do when the occur, but you should be able to set that up with proper bg_writer tuning. -- 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