Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id B13922E0032 for ; Mon, 3 Mar 2008 10:50:37 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 61809-03 for ; Mon, 3 Mar 2008 10:50:28 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from ironport2-out.pppoe.ca (ironport2-out.pppoe.ca [206.248.154.182]) by postgresql.org (Postfix) with ESMTP id 50E212E00DD for ; Mon, 3 Mar 2008 10:50:28 -0400 (AST) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Ao8CACOfy0fO+Igp/2dsb2JhbACsWoEA X-IronPort-AV: E=Sophos;i="4.25,438,1199682000"; d="scan'208";a="15490126" Received: from smtp.pppoe.ca ([65.39.196.238]) by ironport2-out.pppoe.ca with ESMTP; 03 Mar 2008 09:50:25 -0500 Received: from [206.248.136.41] ([206.248.136.41]) by smtp.pppoe.ca (Internet Mail Server v1.0) with ESMTP id JRB14225; Mon, 03 Mar 2008 09:50:25 -0500 Message-ID: <47CC0FD1.7090404@mark.mielke.cc> Date: Mon, 03 Mar 2008 09:48:49 -0500 From: Mark Mielke User-Agent: Thunderbird 2.0.0.12 (X11/20080226) MIME-Version: 1.0 To: Matthew CC: pgsql-performance Subject: Re: How to allocate 8 disks References: <1204285894.11773.33.camel@franck-gusty> <1204296705.11773.51.camel@franck-gusty> <47C88826.4040209@paradise.net.nz> <47C99B3E.4010606@emolecules.com> <20080301130347.0832b323@commandprompt.com> <47C9D05C.3040908@emolecules.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200803/25 X-Sequence-Number: 28979 Matthew wrote: > On Sat, 1 Mar 2008, Craig James wrote: >> Right, I do understand that, but reliability is not a top priority in >> this system. The database will be replicated, and can be reproduced >> from the raw data. > > So what you're saying is: > > 1. Reliability is not important. > 2. There's zero write traffic once the database is set up. > > If this is true, then RAID-0 is the way to go. I think Greg's options > are good. Either: > > 2 discs RAID 1: OS > 6 discs RAID 0: database + WAL > > which is what we're using here (except with more discs), or: > > 8 discs RAID 10: everything Has anybody been able to prove to themselves that RAID 0 vs RAID 1+0 is faster for these sorts of loads? My understanding is that RAID 1+0 *can* reduce latency for reads, but that it relies on random access, whereas RAID 0 performs best for sequential scans? Does PostgreSQL ever do enough random access to make RAID 1+0 shine? Curious. Thanks, mark -- Mark Mielke