From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 21 May 2002 05:04:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 21 May 2002 05:04:39 -0400 Received: from hermine.idb.hist.no ([158.38.50.15]:57354 "HELO hermine.idb.hist.no") by vger.kernel.org with SMTP id ; Tue, 21 May 2002 05:04:39 -0400 Message-ID: <3CEA0D65.DA25FB09@aitel.hist.no> Date: Tue, 21 May 2002 11:03:33 +0200 From: Helge Hafting X-Mailer: Mozilla 4.76 [no] (X11; U; Linux 2.5.12-dj1 i686) X-Accept-Language: no, en, en MIME-Version: 1.0 To: Mike Fedyk CC: linux-kernel@vger.kernel.org Subject: Re: Thoughts on using fs/jbd from drivers/md In-Reply-To: <15587.18828.934431.941516@notabene.cse.unsw.edu.au> <20020516161749.D2410@redhat.com> <20020517182942.GF627@matchmail.com> <20020517193410.W2693@redhat.com> <20020518013537.GH627@matchmail.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Mike Fedyk wrote: > > Doesn't degraded mode imply that there are not any parity > disk(raid4)/stripe(raid5) updates? > Degraded mode means one of the (redundant) disks have failed and isn't used. In raid-4 that might be the parity disk - and then you get the no parity case. But it might be a data disk that failed instead, the missing data will be calculated from parity when needed, and of course parity is modified upon write so information can be stored even though some storage is missing. Raid-5 spreads the parity over all the disks for performance, so wether a missing disk translates to a missing parity stripe or a missing data stripe depends on the exact block number. Helge Hafting