From owner-freebsd-performance@FreeBSD.ORG Mon May 2 13:17:13 2005 Return-Path: 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 BD34416A4D1 for ; Mon, 2 May 2005 13:17:13 +0000 (GMT) Received: from mh1.centtech.com (moat3.centtech.com [207.200.51.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1ECE543D45 for ; Mon, 2 May 2005 13:17:13 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from [10.177.171.220] (neutrino.centtech.com [10.177.171.220]) by mh1.centtech.com (8.13.1/8.13.1) with ESMTP id j42DHC6w004850; Mon, 2 May 2005 08:17:12 -0500 (CDT) (envelope-from anderson@centtech.com) Message-ID: <4276281C.6060209@centtech.com> Date: Mon, 02 May 2005 08:16:12 -0500 From: Eric Anderson User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.5) Gecko/20050325 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Poul-Henning Kamp References: <17442.1115039706@critter.freebsd.dk> In-Reply-To: <17442.1115039706@critter.freebsd.dk> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: ClamAV 0.82/862/Mon May 2 07:24:27 2005 on mh1.centtech.com X-Virus-Status: Clean cc: freebsd-performance@freebsd.org Subject: Re: Very low disk performance on 5.x X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 May 2005 13:17:13 -0000 Poul-Henning Kamp wrote: > In message <427626DC.5030702@centtech.com>, Eric Anderson writes: > > >>Don't mean to be terse here, but I'm talking about the same test done an >>two different RAID5 configurations, with different disks, and not just >>me - other users in this very thread see the same issue.. > > > Uhm, if you are using RAID5 and your requests are not aligned and > sized after the RAID5 you should *expect* read performance to be poor. > > If you your request ends up accessing two different blocks even just > once per stripe, this totally kills performance. Wouldn't this be a problem for writes then too? -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology A lost ounce of gold may be found, a lost moment of time never. ------------------------------------------------------------------------