From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263451AbTDSUWx (ORCPT ); Sat, 19 Apr 2003 16:22:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263452AbTDSUWx (ORCPT ); Sat, 19 Apr 2003 16:22:53 -0400 Received: from h68-147-110-38.cg.shawcable.net ([68.147.110.38]:16126 "EHLO schatzie.adilger.int") by vger.kernel.org with ESMTP id S263451AbTDSUWw (ORCPT ); Sat, 19 Apr 2003 16:22:52 -0400 Date: Sat, 19 Apr 2003 14:33:25 -0600 From: Andreas Dilger To: John Bradford Cc: Stephan von Krawczynski , linux-kernel Subject: Re: Are linux-fs's drive-fault-tolerant by concept? Message-ID: <20030419143325.T26054@schatzie.adilger.int> Mail-Followup-To: John Bradford , Stephan von Krawczynski , linux-kernel References: <20030419185201.55cbaf43.skraw@ithnet.com> <200304192004.h3JK4Sgc000152@81-2-122-30.bradfords.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <200304192004.h3JK4Sgc000152@81-2-122-30.bradfords.org.uk>; from john@grabjohn.com on Sat, Apr 19, 2003 at 09:04:28PM +0100 X-GPG-Key: 1024D/0D35BED6 X-GPG-Fingerprint: 7A37 5D79 BF1B CECA D44F 8A29 A488 39F5 0D35 BED6 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Apr 19, 2003 21:04 +0100, John Bradford wrote: > > > > I wonder whether it would be a good idea to give the linux-fs > > > > (namely my preferred reiser and ext2 :-) some fault-tolerance. I'm not against this in principle, but in practise it is almost useless. Modern disk drives do bad sector remapping at write time, so unless something is terribly wrong you will never see a write error (which is exactly the time that the filesystem could do such remapping). Normally, you will only see an error like this at read time, at which point it is too late to fix. If you do an fsck, it would normally detect the read error and try to write back the repaired data, and cause the device to do remapping. It will not normally be possible to regenerate metadata with anything less than a full fsck (if at all). > > > Fault tollerance should be done at a lower level than the filesystem. > > > > I know it _should_ to live in a nice and easy world. Unfortunately > > real life is different. The simple question is: you have tons of > > low-level drivers for all kinds of storage media, but you have > > comparably few filesystems. To me this sound like the preferred > > place for this type of behaviour can be fs, because all drivers > > inherit the feature if it lives in fs. > > The sort of feature you are describing would really belong in a > separate layer, somewhat analogous to the MD driver, but for defect > management. You could create a virtual block device that has 90% of > the capacity of the real block device, then allocte spare blocks from > the real device if and when blocks failed. Hmm, like the "bad blocks relocation" plugin for EVMS? Cheers, Andreas -- Andreas Dilger http://sourceforge.net/projects/ext2resize/ http://www-mddsp.enel.ucalgary.ca/People/adilger/