From: Pavel Machek Subject: Re: [patch] document flash/RAID dangers Date: Sat, 29 Aug 2009 11:38:04 +0200 Message-ID: <20090829093804.GD1634@ucw.cz> References: <20090825233701.GH4300@elf.ucw.cz> <4A947839.4010601@redhat.com> <20090826000657.GK4300@elf.ucw.cz> <4A947E05.8070406@redhat.com> <20090826002045.GO4300@elf.ucw.cz> <4A9481BE.1030308@redhat.com> <20090826003803.GP4300@elf.ucw.cz> <4A9485A6.1010803@redhat.com> <20090826112121.GD26595@elf.ucw.cz> <4A952370.50603@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: david@lang.hm, 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: Ric Wheeler Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:54298 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751369AbZH2KTD (ORCPT ); Sat, 29 Aug 2009 06:19:03 -0400 Content-Disposition: inline In-Reply-To: <4A952370.50603@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: >> Example I seen went like this: >> >> Drive in raid 5 failed; hot spare was available (no idea about >> UPS). System apparently locked up trying to talk to the failed drive, >> or maybe admin just was not patient enough, so he just powercycled the >> array. He lost the array. >> >> So while most people will not agressively powercycle the RAID array, >> drive failure still provokes little tested error paths, and getting >> unclean shutdown is quite easy in such case. > > Then what we need to document is do not power cycle an array during a > rebuild, right? Yep, that and the fact that you should fsck if you do. > If it wasn't the admin that timed out and the box really was hung (no > drive activity lights, etc), you will need to power cycle/reboot but > then you should not have this active rebuild issuing writes either... Ok, I guess you are right here. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html