From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261473AbTJ2UCE (ORCPT ); Wed, 29 Oct 2003 15:02:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261503AbTJ2UCE (ORCPT ); Wed, 29 Oct 2003 15:02:04 -0500 Received: from gprs194-254.eurotel.cz ([160.218.194.254]:52867 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S261473AbTJ2UCA (ORCPT ); Wed, 29 Oct 2003 15:02:00 -0500 Date: Wed, 29 Oct 2003 21:01:41 +0100 From: Pavel Machek To: John Bradford Cc: Jeff Garzik , Hans Reiser , "Mudama, Eric" , "'Norman Diamond'" , "'Wes Janzen '" , "'Rogier Wolff '" , 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: <20031029200141.GA1941@elf.ucw.cz> References: <785F348679A4D5119A0C009027DE33C105CDB3B0@mcoexc04.mlm.maxtor.com> <3F9D6891.5040300@namesys.com> <3F9D7666.6010504@pobox.com> <200310272003.h9RK32B2001618@81-2-122-30.bradfords.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200310272003.h9RK32B2001618@81-2-122-30.bradfords.org.uk> 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. > > I think that the idea that is floating around is to deliberately ruin > the formatting on part of the drive in order to simulate a bad block. > > Operation of disk drives immediately after a power failiure has been > discussed before, by the way: > > http://marc.theaimsgroup.com/?l=linux-kernel&m=100665153518652&w=2 Well, that looks like pure speculation. BTW I *do* believe that powerfail can make the sector bad. Imagine you bump into bad sector during write, and need to reallocate... Pavel -- When do you have a heart between your knees? [Johanka's followup: and *two* hearts?]