From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262788AbTDUJUc (ORCPT ); Mon, 21 Apr 2003 05:20:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263791AbTDUJUc (ORCPT ); Mon, 21 Apr 2003 05:20:32 -0400 Received: from 81-2-122-30.bradfords.org.uk ([81.2.122.30]:1664 "EHLO 81-2-122-30.bradfords.org.uk") by vger.kernel.org with ESMTP id S262788AbTDUJUb (ORCPT ); Mon, 21 Apr 2003 05:20:31 -0400 From: John Bradford Message-Id: <200304210935.h3L9ZLXc000256@81-2-122-30.bradfords.org.uk> Subject: Re: Are linux-fs's drive-fault-tolerant by concept? To: vda@port.imtp.ilyichevsk.odessa.ua Date: Mon, 21 Apr 2003 10:35:21 +0100 (BST) Cc: john@grabjohn.com (John Bradford), skraw@ithnet.com (Stephan von Krawczynski), linux-kernel@vger.kernel.org In-Reply-To: <200304210900.h3L90vu07375@Port.imtp.ilyichevsk.odessa.ua> from "Denis Vlasenko" at Apr 21, 2003 12:09:07 PM X-Mailer: ELM [version 2.5 PL6] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > > What is so bad about the simple way: the one who wants to write > > > (e.g. fs) and knows _where_ to write simply uses another newly > > > allocated block and dumps the old one on a blacklist. The blacklist > > > only for being able to count them (or get the sector-numbers) in > > > case you are interested. If you weren't you might as well mark them > > > allocated and that's it (which I would presume a _bad_ idea). If > > > there are no free blocks left, well, then the medium is full. And > > > that is just about the only cause for a write error then (if the > > > medium is writeable at all). > > > > Modern disks generally do this kind of thing themselves. By the time > ^^^^^^^^^^^^ > How many times does Stephan need to say it? 'Generally do' > is not enough, because it means 'sometimes they dont'. OK, _ALL_ modern disks do. Name an IDE or SCSI disk on sale today that doesn't retry on write failiure. Forget I said 'Generally do'. > Most filesystems *are* designed with badblock lists and such, > it is possible to teach fs drivers to tolerate write errors > by adding affected blocks to the list and continuing (as opposed > to 'remounted ro, BOOM!'). As usual, this can only happen if someone > will step forward and code it. > > Do you think it would be a Wrong Thing to do? Yes, I do. It achieves nothing useful, and gives people a false sense of security. We have moved on since the 1980s, and I believe that it is now up to the drive firmware, or the block device driver to do this, it has no place in a filesystem. John.