From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263583AbTJQTDm (ORCPT ); Fri, 17 Oct 2003 15:03:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263592AbTJQTDm (ORCPT ); Fri, 17 Oct 2003 15:03:42 -0400 Received: from hq.pm.waw.pl ([195.116.170.10]:47844 "EHLO hq.pm.waw.pl") by vger.kernel.org with ESMTP id S263583AbTJQTDh (ORCPT ); Fri, 17 Oct 2003 15:03:37 -0400 To: John Bradford Cc: Rogier Wolff , Norman Diamond , Hans Reiser , Wes Janzen , linux-kernel@vger.kernel.org Subject: Re: Blockbusting news, this is important (Re: Why are bad disk sectors numbered strangely, and what happens to them?) References: <32a101c3916c$e282e330$5cee4ca5@DIAMONDLX60> <200310131014.h9DAEwY3000241@81-2-122-30.bradfords.org.uk> <33a201c39174$2b936660$5cee4ca5@DIAMONDLX60> <20031014064925.GA12342@bitwizard.nl> <3F8BA037.9000705@sbcglobal.net> <3F8BBC08.6030901@namesys.com> <11bf01c39492$bc5307c0$3eee4ca5@DIAMONDLX60> <20031017102436.GB10185@bitwizard.nl> <200310171049.h9HAnBbO000594@81-2-122-30.bradfords.org.uk> From: Krzysztof Halasa Date: 17 Oct 2003 13:24:10 +0200 In-Reply-To: <200310171049.h9HAnBbO000594@81-2-122-30.bradfords.org.uk> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org John Bradford writes: > Besides, are you positive that you always got the correct data off the > disk? See the discussions about hashing algorithms - maybe the drive > simply returned data that had an additional bit flipped and wasn't > identified as bad. One bit? No chance. The same as with ECC RAM - one bit error will always be detected. > If you are having to try over 1000 times from > userspace, the drive is in a bad way. You shouldn't really make > assumptions that you do usually, (that the error correction is good > enough to ensure bad data isn't returned as good data). If you are > recovering data from a spreadsheet, for example, the errors could go > unnoticed, but have catastrophic results. Then you have to abandon using any hard drivers. Or computers at all. Well, mirrors (with read-and-compare) are probably good enough for you, but it has to be done at application level. > Of course you will - it's remapped, the data isn't overwritten! You > may need more advanced tools, = in practice, it's lost. Have you seen such tools? > but you can still seek the heads to that > part of the platter and get data from the head-amp. Just because you > couldn't use your simple method anymore is real reason to argue > against fixing the problem. against _changing_ the problem (it doesn't go away), breaking things which are now sane. > This may be more sensible, but not for the reasons you are suggesting, > and not in the way that you are suggesting. Then note that a drive can be temporarily unable to read most of the data - due to, say, incorrect supply voltage or very high level of electromagnetic interferences. Would you like to trash _all_ your data in such case automatically? > Suspect drive? Bin it. Do you really not value your data enough to > do that? Do you really not value your data enough to mark it as inaccessible? If it comes to non-standard recovery then you should rather go for backups. -- Krzysztof Halasa, B*FH