From owner-freebsd-performance@FreeBSD.ORG Fri Sep 23 03:05:09 2005 Return-Path: X-Original-To: freebsd-performance@freebsd.org Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6744416A41F for ; Fri, 23 Sep 2005 03:05:09 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id 020C843D46 for ; Fri, 23 Sep 2005 03:05:08 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id 67CFF5EE5; Thu, 22 Sep 2005 23:05:08 -0400 (EDT) Received: from pi.codefab.com ([127.0.0.1]) by localhost (pi.codefab.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 36762-08; Thu, 22 Sep 2005 23:05:07 -0400 (EDT) Received: from [192.168.1.3] (pool-68-161-68-11.ny325.east.verizon.net [68.161.68.11]) by pi.codefab.com (Postfix) with ESMTP id 560F95D14; Thu, 22 Sep 2005 23:05:07 -0400 (EDT) Message-ID: <433370E4.8060708@mac.com> Date: Thu, 22 Sep 2005 23:05:08 -0400 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.11) Gecko/20050728 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Francisco References: <63f9d26505090417183dff415e@mail.gmail.com> <431C683B.1080803@mac.com> <20050922215326.B50836@zoraida.natserv.net> In-Reply-To: <20050922215326.B50836@zoraida.natserv.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: amavisd-new at codefab.com Cc: Jeff Tchang , freebsd-performance@freebsd.org Subject: Re: 3Ware 7500-4 Slow X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 23 Sep 2005 03:05:09 -0000 Francisco wrote: > On Mon, 5 Sep 2005, Chuck Swiger wrote: >> Small writes are pretty much the worst-case scenario for RAID-5, > > Such as mail servers? So-so. RAID-5 is okay on a IMAP reader box, it's not so good for a pure SMTP relay, especially one that does virus scanning. > How about for a DB server which is mostly read only? If your DB claims to support a RAID-5 configuration-- some DBs will change their caching behavior to avoid thrashing a RAID-5 volume as much-- it might be OK. If you're going to run a big DB, you really ought to be designing the disk layout according to what the DB vendor recommends. >> normal to see a very significant performance drop-- by up to an order >> of magnitude-- from the performance of a bare drive. > > At which point Raid 5 starts to perform better? > 6,8,10 drives? Better for small writes? Never. Although good hardware and lots of RAM to cache with can help a lot. RAID systems have bus limitations on how wide they can go in terms of # of drives, also in how much real bus bandwidth is available for very wide configs. 8 drives is a common maximum width. > How about RAID 10 for a DB server? This is a much better choice, close to ideal. > I have been trying to convince the "powers that be" that SCSI would be > much better.. but the price difference is just too astronomical for the > capacities we need (500GB to 2 TB) > > Even 10K RPM IDE drives seem like would be a problem since they are > mostly small in size. Ten 72's would be in the right ballpark, that's about $2000. Ten of the cheapest reasonable 80GB ATA drives would be about $800. You could always ask: "How much is your data worth to your company, again?" You can get 146's for about $500 and even 300GB SCSI-3 drives exist. -- -Chuck