From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263806AbTJ1BWN (ORCPT ); Mon, 27 Oct 2003 20:22:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263807AbTJ1BWN (ORCPT ); Mon, 27 Oct 2003 20:22:13 -0500 Received: from gprs192-78.eurotel.cz ([160.218.192.78]:6273 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S263806AbTJ1BWL (ORCPT ); Mon, 27 Oct 2003 20:22:11 -0500 Date: Tue, 28 Oct 2003 02:21:43 +0100 From: Pavel Machek To: Jeff Garzik Cc: Hans Reiser , "Mudama, Eric" , "'Norman Diamond'" , "'Wes Janzen '" , "'Rogier Wolff '" , "'John Bradford '" , linux-kernel@vger.kernel.org, nikita@namesys.com, "'Pavel Machek '" , "'Justin Cormack '" , "'Vitaly Fertman '" , "'Krzysztof Halasa '" Subject: Re: Blockbusting news, results get worse Message-ID: <20031028012143.GA427@elf.ucw.cz> References: <785F348679A4D5119A0C009027DE33C105CDB3B0@mcoexc04.mlm.maxtor.com> <3F9D6891.5040300@namesys.com> <3F9D7666.6010504@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3F9D7666.6010504@pobox.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > >>or put it under heavy write workload and remove > >>power. > >> > >Can you tell us more about what really happens to disk drives when the > >power is cut while a block is being written? We engage in a lot of > >uninformed speculation, and it would be nice if someone who really knows > >told us.... > > > >Do drives have enough capacitance under normal conditions to finish > >writing the block? Does ECC on the drive detect that the block was bad > >and so we don't need to detect it in the FS? > > > Does it really matter to speculate about this? > > If you don't FLUSH CACHE, you have no guarantees your data is on the > platter. Well, even without FLUSH CACHE, you can expect that sector being writen during powerfail either contains old data *or* new data. If sector can become unreadable after powerfail, I guess journaling people would like to know, and if powerfail may mean adjacent (or even unrelated?) sectors to be damaged, everyone needs to know... Pavel -- When do you have a heart between your knees? [Johanka's followup: and *two* hearts?]