From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756530AbZHZAMY (ORCPT ); Tue, 25 Aug 2009 20:12:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755972AbZHZAMW (ORCPT ); Tue, 25 Aug 2009 20:12:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:8411 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756238AbZHZAMU (ORCPT ); Tue, 25 Aug 2009 20:12:20 -0400 Message-ID: <4A947DA9.2080906@redhat.com> Date: Tue, 25 Aug 2009 20:11:21 -0400 From: Ric Wheeler User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.1) Gecko/20090814 Fedora/3.0-2.6.b3.fc11 Lightning/1.0pre Thunderbird/3.0b3 MIME-Version: 1.0 To: Pavel Machek CC: 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 Subject: Re: [patch] ext2/3: document conditions when reliable operation is possible References: <20090824230036.GK29763@elf.ucw.cz> <20090825000842.GM17684@mit.edu> <20090825094244.GC15563@elf.ucw.cz> <4A93E908.6050908@redhat.com> <20090825211515.GA3688@elf.ucw.cz> <4A9468E8.607@redhat.com> <20090825225114.GE4300@elf.ucw.cz> <4A946DD1.8090906@redhat.com> <20090825232601.GF4300@elf.ucw.cz> <4A947682.2010204@redhat.com> <20090825235359.GJ4300@elf.ucw.cz> In-Reply-To: <20090825235359.GJ4300@elf.ucw.cz> 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 08/25/2009 07:53 PM, Pavel Machek wrote: >> Why don't you hold all of your most precious data on that single S-ATA >> drive for five year on one box and put a second copy on a small RAID5 >> with ext3 for the same period? >> >> Repeat experiment until you get up to something like google scale or the >> other papers on failures in national labs in the US and then we can have >> an informed discussion. > > I'm not interested in discussing statistics with you. I'd rather discuss > fsync() and storage design issues. > > ext3 is designed to work on single SATA disks, and it is not designed > to work on flash cards/degraded MD RAID5s, as Ted acknowledged. You are simply incorrect, Ted did not say that ext3 does not work with MD raid5. > > Because that fact is non obvious to the users, I'd like to see it > documented, and now have nice short writeup from Ted. > > If you want to argue that ext3/MD RAID5/no UPS combination is still > less likely to fail than single SATA disk given part fail > probabilities, go ahead and present nice statistics. Its just that I'm > not interested in them. > Pavel > That is a proven fact and a well published one. If you choose to ignore published work (and common sense) that RAID makes you lose data less than non-RAID, why should anyone care what you write? Ric