From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: If I have a single bad sector, how many failed reads should simple dd report? Date: Fri, 09 Jul 2010 21:19:21 -0400 Message-ID: <4C37CA99.1040104@teksavvy.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from ironport2-out.teksavvy.com ([206.248.154.183]:21008 "EHLO ironport2-out.pppoe.ca" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751186Ab0GJBTX (ORCPT ); Fri, 9 Jul 2010 21:19:23 -0400 In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Greg Freemyer Cc: IDE/ATA development list , Mark Lord On 09/07/10 03:04 PM, Greg Freemyer wrote: .. >> When I re-ran it, /var/log/messages reported 10 bad logical blocks. >> And even worse, dd reported 20 bad blocks. I examined the data dd >> read and it had 80KB of zero'ed out data. So that's 160 sectors worth >> of data lost because of a single bad sector. At most I was expecting >> 4KB of zero'ed out data. .. That's just the standard, undesirable result of the current SCSI EH when used with libata for (mainly) desktop computers. I have patches (against older kernels) to fix it, but have yet to get both myself and James B. interested enough simultaneously to actually get the kernel fixed. :) .. > cmp -bl clean.dd corrupt.dd> delta.log > > Looking at delta.log, the bytes start disagreeing 4 bytes prior to the > sector boundary. How can that be? .. Dunno. That could be a different problem. I've seen the odd scattered report of data corruption on ext3/ext4 with large data sets, but don't know what the root causes were. Cheers