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 B83849DCA64 for ; Tue, 31 Jan 2006 19:10:16 -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 77940-10 for ; Tue, 31 Jan 2006 19:10:18 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from peufeu.com (boutiquenumerique.com [82.67.9.10]) by postgresql.org (Postfix) with ESMTP id 5375F9DCA5E for ; Tue, 31 Jan 2006 19:10:14 -0400 (AST) Received: (qmail 16073 invoked from network); 1 Feb 2006 00:11:06 +0100 Received: from boutiquenumerique.com (HELO apollo13) (82.67.9.10) by boutiquenumerique.com with SMTP; 1 Feb 2006 00:11:06 +0100 To: "Luke Lonergan" , "Jeffrey W. Baker" , pgsql-performance@postgresql.org Subject: Re: Huge Data sets, simple queries References: Message-ID: Date: Wed, 01 Feb 2006 00:11:05 +0100 From: PFC Content-Type: text/plain; format=flowed; delsp=yes; charset=utf-8 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Opera M2/8.51 (Linux, build 1462) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.06 required=5 tests=[AWL=0.060] X-Spam-Score: 0.06 X-Spam-Level: X-Archive-Number: 200601/496 X-Sequence-Number: 16974 >> Linux does balanced reads on software >> mirrors. I'm not sure why you think this can't improve bandwidth. It >> does improve streaming bandwidth as long as the platter STR is more than >> the bus STR. > > ... Prove it. > (I have a software RAID1 on this desktop machine) It's a lot faster than a single disk for random reads when more than 1 thread hits the disk, because it distributes reads to both disks. Thus, applications start faster, and the machine is more reactive even when the disk is thrashing. Cron starting a "updatedb" is less painful. It's cool for desktop use (and of course it's more reliable). However large reads (dd-style) are just the same speed as 1 drive. I guess you'd need a humongous readahead in order to read from both disks.