From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rik van Riel Subject: Re: [patch] ext2/3: document conditions when reliable operation is possible Date: Wed, 26 Aug 2009 23:29:56 -0400 Message-ID: <4A95FDB4.3050904@redhat.com> References: <20090824212518.GF29763@elf.ucw.cz> <20090824223915.GI17684@mit.edu> <20090824230036.GK29763@elf.ucw.cz> <20090825000842.GM17684@mit.edu> <20090825094244.GC15563@elf.ucw.cz> <4A93E908.6050908@redhat.com> <20090825211515.GA3688@elf.ucw.cz> <19092.28371.793339.764701@notabene.brown> <20090825234454.GI4300@elf.ucw.cz> <4A94B529.1080308@redhat.com> <20090826111537.GB26595@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Neil Brown , 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, corbet@lwn.net To: Pavel Machek Return-path: In-Reply-To: <20090826111537.GB26595@elf.ucw.cz> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Pavel Machek wrote: > Hi! > >>> Ok, can you help? Having a piece of MD documentation explaining the >>> "powerfail nukes entire stripe" and how current filesystems do not >>> deal with that would be nice, along with description when exactly that >>> happens. >> Except of course for the inconvenient detail that a power >> failure on a degraded RAID 5 array does *NOT* nuke the >> entire stripe. > > Ok, you are right. It will nuke unrelated sector somewhere on the > stripe (one that is "old" and was not recently written) -- which is > still something ext3 can not reliably handle. Not quite unrelated. The "nuked" sector will be the one that used to live on the disk that is broken and no longer a part of the RAID 5 array. I wouldn't qualify a missing hard disk as a software issue... -- All rights reversed.