From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753775AbZHaSAW (ORCPT ); Mon, 31 Aug 2009 14:00:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751937AbZHaSAV (ORCPT ); Mon, 31 Aug 2009 14:00:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18503 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751808AbZHaSAU (ORCPT ); Mon, 31 Aug 2009 14:00:20 -0400 Message-ID: <4A9C0FE2.8020607@redhat.com> Date: Mon, 31 Aug 2009 14:01:06 -0400 From: Ric Wheeler User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090806 Fedora/3.0-3.8.b3.fc12 Thunderbird/3.0b3 MIME-Version: 1.0 To: Jesse Brandeburg CC: Theodore Tso , Pavel Machek , NeilBrown , Rob Landley , Florian Weimer , Goswin von Brederlow , kernel list , Andrew Morton , mtk.manpages@gmail.com, rdunlap@xenotime.net, linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org, corbet@lwn.net Subject: Re: raid is dangerous but that's secret (was Re: [patch] ext2/3: document conditions when reliable operation is possible) References: <20090824212518.GF29763@elf.ucw.cz> <4A947682.2010204@redhat.com> <200908262253.17886.rob@landley.net> <4A967175.5070700@redhat.com> <20090827221319.GA1601@ucw.cz> <4A9733C1.2070904@redhat.com> <20090828064449.GA27528@elf.ucw.cz> <20090828120854.GA8153@mit.edu> <20090830075135.GA1874@ucw.cz> <20090830152023.GB23828@mit.edu> <4807377b0908311049id9a2167r937bc8447c2b3546@mail.gmail.com> In-Reply-To: <4807377b0908311049id9a2167r937bc8447c2b3546@mail.gmail.com> 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 On 08/31/2009 01:49 PM, Jesse Brandeburg wrote: > On Sun, Aug 30, 2009 at 8:20 AM, Theodore Tso wrote: >> So we *do* have the warning light; the problem is that just as some >> people may not realize that "check brakes" means, "YOU COULD DIE", >> some people may not realize that "hard drive failure; RAID array >> degraded" could mean, "YOU COULD LOSE DATA". >> >> Fortunately, for software RAID, this is easily solved; if you are so >> concerned, why don't you submit a patch to mdadm adjusting the e-mail >> sent to the system administrator when the array is in a degraded >> state, such that it states, "YOU COULD LOSE DATA". I would gently >> suggest to you this would be ***far*** more effective that a patch to >> kernel documentation. > > In the case of a degraded array, could the kernel be more proactive > (or maybe even mdadm) and have the filesystem remount itself withOUT > journalling enabled? This seems on the surface to be possible, but I > don't know the internal particulars that might prevent/allow it. This a misconception - with or without journalling, you are open to a second failure during a RAID rebuild. Also note that by default, ext3 does not mount with barriers turned on. Even if you mount with barriers, MD5 does not handle barriers, so you stand to lose a lot of data if you have a power outage. Ric