From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 17 May 2002 14:30:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 17 May 2002 14:30:12 -0400 Received: from adsl-63-194-239-202.dsl.lsan03.pacbell.net ([63.194.239.202]:48145 "EHLO mmp-linux.matchmail.com") by vger.kernel.org with ESMTP id ; Fri, 17 May 2002 14:30:11 -0400 Date: Fri, 17 May 2002 11:29:42 -0700 From: Mike Fedyk To: "Stephen C. Tweedie" Cc: Neil Brown , linux-kernel@vger.kernel.org Subject: Re: Thoughts on using fs/jbd from drivers/md Message-ID: <20020517182942.GF627@matchmail.com> Mail-Followup-To: "Stephen C. Tweedie" , Neil Brown , linux-kernel@vger.kernel.org In-Reply-To: <15587.18828.934431.941516@notabene.cse.unsw.edu.au> <20020516161749.D2410@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.3.28i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 16, 2002 at 04:17:49PM +0100, Stephen C. Tweedie wrote: > Hi, > > On Thu, May 16, 2002 at 03:54:20PM +1000, Neil Brown wrote: > > The basic idea is to provide journaling for md/RAID arrays. There > > are two reasons that one might want to do this: > > 1/ crash recovery. Both raid1 and raid5 need to reconstruct the > > redundancy after a crash. For a degraded raid5 array, this is not > > possible and you can suffer undetected data corruption. > > If we have a journal of recent changes we can avoid the > > reconstruction and the risk of corruption. > > Right. The ability of soft raid5 to lose data in degraded mode over a > reboot (including data that was not being modified at the time of the > crash) is something that is not nearly as widely understood as it > should be, and I'd love for us to do something about it. Are there workarounds to avoid this problem? What does it take to trigger the corruption? I ask this because I have used a degraded raid5 because the source drive would become a member, but I needed to copy the data first. While doing so, I had to reboot a couple times to reconfigure the boot loader. All seems to be working fine on the system today though. Thanks, Mike