From: Greg Freemyer Subject: Re: [patch] ext2/3: document conditions when reliable operation is possible Date: Mon, 24 Aug 2009 17:11:56 -0400 Message-ID: <87f94c370908241411r45079c5cx3fc737cf4c3f7d1e@mail.gmail.com> References: <200903121413.04434.rob@landley.net> <200903161426.24904.rob@landley.net> <20090323104525.GA17969@elf.ucw.cz> <87ljqn82zc.fsf@frosties.localdomain> <20090824093143.GD25591@elf.ucw.cz> <82k50tjw7u.fsf@mid.bfk.de> <20090824130125.GG23677@mit.edu> <20090824195159.GD29763@elf.ucw.cz> <4A92F6FC.4060907@redhat.com> <20090824205209.GE29763@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Ric Wheeler , Theodore Tso , Florian Weimer , Goswin von Brederlow , Rob Landley , kernel list , Andrew Morton , mtk.manpages@gmail.com, rdunlap@xenotime.net, linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org To: Pavel Machek Return-path: Received: from qw-out-2122.google.com ([74.125.92.26]:8599 "EHLO qw-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752621AbZHXVLz (ORCPT ); Mon, 24 Aug 2009 17:11:55 -0400 In-Reply-To: <20090824205209.GE29763@elf.ucw.cz> Sender: linux-ext4-owner@vger.kernel.org List-ID: > The papers show failures in "once a year" range. I have "twice a > minute" failure scenario with flashdisks. > > Not sure how often "degraded raid5 breaks ext3 atomicity" would bite, > but I bet it would be on "once a day" scale. > I agree it should be documented, but the ext3 atomicity issue is only an issue on unexpected shutdown while the array is degraded. I surely hope most people running raid5 are not seeing that level of unexpected shutdown, let along in a degraded array, If they are, the atomicity issue pretty strongly says they should not be using raid5 in that environment. At least not for any filesystem I know. Having writes to LBA n corrupt LBA n+128 as an example is pretty hard to design around from a fs perspective. Greg