Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761673AbYCAUAp (ORCPT ); Sat, 1 Mar 2008 15:00:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756961AbYCAUAe (ORCPT ); Sat, 1 Mar 2008 15:00:34 -0500 Received: from mail.tmr.com ([64.65.253.246]:54854 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756904AbYCAUAd (ORCPT ); Sat, 1 Mar 2008 15:00:33 -0500 Message-ID: <47C9B6CD.3040709@tmr.com> Date: Sat, 01 Mar 2008 15:04:29 -0500 From: Bill Davidsen Organization: TMR Associates Inc, Schenectady NY 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: Andreas Dilger CC: Tomasz Chmielewski , Theodore Tso , Andi Kleen , LKML , LKML , linux-raid@vger.kernel.org Subject: Re: very poor ext3 write performance on big filesystems? References: <47B980AC.2080806@wpkg.org> <20080218141640.GC12568@mit.edu> <47C54773.4040402@wpkg.org> <20080227200335.GB9331@webber.adilger.int> In-Reply-To: <20080227200335.GB9331@webber.adilger.int> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1271 Lines: 29 Andreas Dilger wrote: > I'm CCing the linux-raid mailing list, since I suspect they will be > interested in this result. > > I would suspect that the "journal guided RAID recovery" mechanism > developed by U.Wisconsin may significantly benefit this workload > because the filesystem journal is already recording all of these > block numbers and the MD bitmap mechanism is pure overhead. > Thanks for sharing these numbers. I think use of a bitmap is one of those things which people have to configure to match their use, certainly using a larger bitmap seems to reduce the delays, using an external bitmap certainly help, especially on an SSD. But on a large array, without a bitmap, performance can be compromised for hours during recovery, so the administrator must decide if normal case performance is more important than worst case performance. -- Bill Davidsen "Woe unto the statesman who makes war without a reason that will still be valid when the war is over..." Otto von Bismark -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/