From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030337AbWARPTy (ORCPT ); Wed, 18 Jan 2006 10:19:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030342AbWARPTy (ORCPT ); Wed, 18 Jan 2006 10:19:54 -0500 Received: from host233.omnispring.com ([69.44.168.233]:52447 "EHLO iradimed.com") by vger.kernel.org with ESMTP id S1030337AbWARPTy (ORCPT ); Wed, 18 Jan 2006 10:19:54 -0500 Message-ID: <43CE5C7A.5060608@cfl.rr.com> Date: Wed, 18 Jan 2006 10:19:22 -0500 From: Phillip Susi User-Agent: Thunderbird 1.5 (Windows/20051201) MIME-Version: 1.0 To: Max Waterman CC: linux-kernel@vger.kernel.org Subject: Re: io performance... References: <43CB4CC3.4030904@fastmail.co.uk> <43CD2405.4070902@cfl.rr.com> <43CDED23.5060701@fastmail.co.uk> In-Reply-To: <43CDED23.5060701@fastmail.co.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 18 Jan 2006 15:20:10.0511 (UTC) FILETIME=[ABF669F0:01C61C42] X-TM-AS-Product-Ver: SMEX-7.2.0.1122-3.51.1032-14213.000 X-TM-AS-Result: No--4.300000-5.000000-31 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Right, the kernel does not know how many disks are in the array, so it can't automatically increase the readahead. I'd say increasing the readahead manually should solve your throughput issues. Max Waterman wrote: > > I left the stripe size at the default, which, I believe, is 64K bytes; > same as your fakeraid below. > > I did play with 'blockdev --setra' too. > > I noticed it was 256 with a single disk, and, with s/w raid, it > increased by 256 for each extra disk in the array. IE for the raid 0 > array with 4 drives, it was 1024. > > With h/w raid, however, it did not increase when I added disks. Should I > use 'blockdev --setra 320' (ie 64 x 5 = 320, since we're now running > RAID5 on 5 drives)? >