Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261686AbVEPPDH (ORCPT ); Mon, 16 May 2005 11:03:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261688AbVEPPDF (ORCPT ); Mon, 16 May 2005 11:03:05 -0400 Received: from krusty.dt.E-Technik.Uni-Dortmund.DE ([129.217.163.1]:40864 "EHLO mail.dt.e-technik.uni-dortmund.de") by vger.kernel.org with ESMTP id S261686AbVEPPAB (ORCPT ); Mon, 16 May 2005 11:00:01 -0400 Date: Mon, 16 May 2005 16:59:54 +0200 From: Matthias Andree To: Mark Lord Cc: Matthias Andree , linux-kernel@vger.kernel.org Subject: Re: Linux does not care for data integrity Message-ID: <20050516145954.GB949@merlin.emma.line.org> Mail-Followup-To: Mark Lord , linux-kernel@vger.kernel.org References: <200505151121.36243.gene.heskett@verizon.net> <20050515152956.GA25143@havoc.gtf.org> <20050516.012740.93615022.okuyamak@dd.iij4u.or.jp> <42877C1B.2030008@pobox.com> <20050516110203.GA13387@merlin.emma.line.org> <4288A4CA.7000009@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4288A4CA.7000009@rtr.ca> X-PGP-Key: http://home.pages.de/~mandree/keys/GPGKEY.asc User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1911 Lines: 40 On Mon, 16 May 2005, Mark Lord wrote: > Most of us want longer lifespan and 2X the performance from our hardware, > and use UPSs to guarantee continuous power & survivability. Which is a different story and doesn't protect from dying power supply units. I have replaced several PSUs that died "in mid-flight" and that were not overloaded. UPS isn't going to help in that case. Of course you can use a redundant PSU, redundant UPS - but that's easily more than a battery-backed up cache on a decent RAID controller - since drive failure will also toast file systems. > Others want to live more dangerously on the power supply end, > but still be safe on the filesystem end -- no guarantees there, > even with "hdparm -W0" to disable the on-drive cache. As long as one can rely on the kernel scheduling writes in the proper order, no problem that I'd see. ext3 has apparently been doing this for a long time in the default options, and I have yet to see ext3 corruption (except for massive hardware failure such as b0rked non-ECC RAM or a harddisk that crashed its heads). > Pulling power from a writing drive is ALWAYS a bad idea, > and can permanently corrupt the track/cylinder that was being > written. This will toast a filesystem regardless of how careful > or proper the write flushes were done. Most drive manufacturers make more extensive guarantees about what gets NOT damaged when a write is interrupted by power loss, and are careful to turn the write current off pretty soon on power loss. None of the OEM manuals I looked at advised that data that was already on disk would be damaged beyond the block that was being written. -- Matthias Andree - 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/