From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261728AbVF0Ovc (ORCPT ); Mon, 27 Jun 2005 10:51:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261729AbVF0Osx (ORCPT ); Mon, 27 Jun 2005 10:48:53 -0400 Received: from THUNK.ORG ([69.25.196.29]:8665 "EHLO thunker.thunk.org") by vger.kernel.org with ESMTP id S262119AbVF0Mnr (ORCPT ); Mon, 27 Jun 2005 08:43:47 -0400 Date: Mon, 27 Jun 2005 08:42:55 -0400 From: "Theodore Ts'o" To: Markus T?rnqvist Cc: Horst von Brand , David Masover , Alan Cox , Hans Reiser , Jeff Garzik , Christoph Hellwig , Andrew Morton , Linux Kernel Mailing List , ReiserFS List Subject: Re: reiser4 plugins Message-ID: <20050627124255.GB6280@thunk.org> Mail-Followup-To: Theodore Ts'o , Markus T?rnqvist , Horst von Brand , David Masover , Alan Cox , Hans Reiser , Jeff Garzik , Christoph Hellwig , Andrew Morton , Linux Kernel Mailing List , ReiserFS List References: <42BB7B32.4010100@slaphack.com> <200506240334.j5O3YowB008100@laptop11.inf.utfsm.cl> <20050627092138.GD11013@nysv.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050627092138.GD11013@nysv.org> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 27, 2005 at 12:21:38PM +0300, Markus T?rnqvist wrote: > On Thu, Jun 23, 2005 at 11:34:50PM -0400, Horst von Brand wrote: > >David Masover wrote: > > >> I think Hans (or someone) decided that when hardware stops working, it's > >> not the job of the FS to compensate, it's the job of lower layers, or > >> better, the job of the admin to replace the disk and restore from > >> backups. > >Handling other people's data this way is just reckless irresponsibility. > >Sure, you can get high performance if you just forego some of your basic > >responsibilities. > > Your honest-to-bog opinion is that the FS vendor is responsible for > the admin not taking backups or the hardware vendor shipping crap? > > *still trying to understand how that can be* Most Linux users are using PC-class hardware. And Ted's First Law of PC-Class Hardware is: "Most of it is crap". And then there's Ted's Second Law, "Too many system administrators don't do backups". This is because most system admins are users who've never been trained to be a sysadmin, or who haven't (yet) had weeks or months of works disappear after a hardware failure. So it's a matter of matching the filesystem to the needs of the user. If you have a filesystem which is blazingly fast, but which at the slightest sign of trouble, trashes your data, versus one which is fast but perhaps not-so-fast as the other filesystem, but which is much more reliable, which would you choose? XFS has similar issues where it assumes that hardware has powerfail interrupts, and that the OS can use said powerfail interrupt to stop DMA's in its tracks on an power failure, so that you don't have garbage written to key filesystem data structures when the memory starts suffering from the dropping voltage on the power bus faster than the DMA engine or the disk drives. So XFS is a great filesystem --- but you'd better be running it on a UPS, or on a system which has power fail interrupts and an OS that knows what to do. Ext3, because it does physical block journalling, does not suffer from this problem. (Yes, Resierfs uses logical journalling as well, so it suffers from the same problem.) So perhaps it's not the job of the FS vendor to be responsible for crap hardware or lazy sysadmins that don't do backups. But a system administrator who knows that he doesn't do backups frequently enough, or is running on cheap, crap hardware, would be wise to consider carefully which filesystem he/she wants to use given the systems configuration and his backup habits. Me, I'll go for the robust filesystem, just on general principles. As a friend from the large-scale enterprise storage world once put it, "Performance is Job 2. Robustness is Job #1." (Of course, if you want to put your fragile filesystem on a multi-million dollar enterprise storage system such as an IBM Shark or an EMC Symmetrix box, I'm sure IBM or EMC will be happy to sell you one. :-) - Ted