From: Pavel Machek Subject: Re: [testcase] test your fs/storage stack (was Re: [patch] ext2/3: document conditions when reliable operation is possible) Date: Thu, 3 Sep 2009 10:55:10 +0200 Message-ID: <20090903085510.GE3793@elf.ucw.cz> References: <20090826001645.GN4300@elf.ucw.cz> <20090902201210.GC1840@ucw.cz> <4A9ED8AB.5080003@redhat.com> <200909021800.51096.rob@landley.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Rob Landley , Ric Wheeler , Theodore Tso , Florian Weimer , Goswin von Brederlow , kernel list , Andrew Morton , mtk.manpages@gmail.com, rdunlap@xenotime.net, linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org, corbet@lwn.net To: david@lang.hm Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-doc-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Hi! >> However, thinking about how to _fix_ a problem is predicated on acknowledging >> that there actually _is_ a problem. "The hardware is not physically damaged >> but your data was lost" sounds to me like a software problem, and thus >> something software could at least _attempt_ to address. "There's millions of >> 'em, Linux can't cope" doesn't seem like a useful approach. > > no other OS avoids this problem either. > > I actually don't see how you can do this from userspace, because when you > write to the device you have _no_ idea where on the device your data will > actually land. It certainly is not easy. Self-correcting codes could probably be used, but that would be very special, very slow, and very non-standard. (Basically... we could design filesystem so that it would survive damage of arbitrarily 512K on disk -- using self-correcting codes in CD-like manner). I'm not sure if it would be practical. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html