From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755254AbYE1Wsz (ORCPT ); Wed, 28 May 2008 18:48:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753467AbYE1Wsp (ORCPT ); Wed, 28 May 2008 18:48:45 -0400 Received: from mail.tmr.com ([64.65.253.246]:48975 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753322AbYE1Wso convert rfc822-to-8bit (ORCPT ); Wed, 28 May 2008 18:48:44 -0400 Message-ID: <483DE40D.8090608@tmr.com> Date: Wed, 28 May 2008 19:00:29 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 To: Alan Cox CC: =?UTF-8?B?SmVucyBCw6Rja21hbg==?= , Justin Piszcz , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, xfs@oss.sgi.com Subject: Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++) References: <95711f160805280934y77ed7d91tec5aeb531bf8013c@mail.gmail.com> <20080528195752.0cdcbc6d@core> In-Reply-To: <20080528195752.0cdcbc6d@core> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alan Cox wrote: > On Wed, 28 May 2008 18:34:00 +0200 > "Jens Bäckman" wrote: > >> On Wed, May 28, 2008 at 10:53 AM, Justin Piszcz wrote: >>> Results: >>> >>> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.html >>> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.txt >> Either the RAID 1 read speed must be wrong, or something is odd in the >> Linux implementation. There's six drives that can be used for reading >> at the same time, as they contain the very same data. 63MB/s >> sequential looks like what you would get from a single drive. > > Which is fairly typical of a cheap desktop PC where the limitation is the > memory and PCI bridge as much as the drive. > I really don't think that's any part of the issue, the same memory and bridge went 4-5x faster in other read cases. The truth is that the raid-1 performance is really bad, and it's the code causing it AFAIK. If you track the actual io it seems to read one drive at a time, in order, without overlap. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot