Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752923AbWKCBea (ORCPT ); Thu, 2 Nov 2006 20:34:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752925AbWKCBea (ORCPT ); Thu, 2 Nov 2006 20:34:30 -0500 Received: from artax.karlin.mff.cuni.cz ([195.113.31.125]:37526 "EHLO artax.karlin.mff.cuni.cz") by vger.kernel.org with ESMTP id S1752923AbWKCBe3 (ORCPT ); Thu, 2 Nov 2006 20:34:29 -0500 Date: Fri, 3 Nov 2006 02:34:28 +0100 (CET) From: Mikulas Patocka To: Grzegorz Kulewski Cc: linux-kernel@vger.kernel.org Subject: Re: New filesystem for Linux In-Reply-To: Message-ID: References: X-Personality-Disorder: Schizoid MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2189 Lines: 54 >> There was discussion about it here some times ago, and I think the result >> was that the IDE bus is reset prior to capacitors discharge and total loss >> of power and disk has enough time to finish a sector --- but if you have >> crap power supply (doesn't signal power loss), crap motherboard (doesn't >> reset bus) or crap disk (doesn't respond to reset), it can fail. > > Hmm, maybe. But I think I saw couple of such bad sectors that were only bad > because of power loss in the wild. > > >> BTW. reiserfs and xfs depend on this feature too. ext3 is the only one that >> doesn't. > > Well, at least for XFS everybody tell that it should be used with UPS only if > you really care about your data. I think it has something to do with heavy > in-RAM caching this filesystem does. System is allowed to cache anything unless sync/fsync is called. Someone told that XFS has some bugs that if crashed incorrectly, it can lose already synced data ... don't know. Plus it has that infamous feature (not a bug) that it commits size-increase but not data and you see zero-filed files. > Anyway, it looks strange to list something very fragile and potentially not > existing in the requirements... :-) Better to list it than quitly depend on it like ext2/fat/reiser/xfs/ (maybe jfs?) do. > Could you explain where exactly do you depend on this requirement? And what > could happen if it is not true? If you write a file in a directory and the sector is unwritable upon write & crash, you lose those few files near it. Just the similar way you would lose 4 files in inode table on ext2 in this case. > Thanks, > > Grzegorz Kulewski > > > PS. Do you have any benchmarks of your filesystem? Did you do any longer > automated tests to prove it is not going to loose data to easily? I have, I may find them and post them. (but the university wants me to post them to some conference, so I should keep them secret :-/) Mikulas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/