From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933840AbWLIKQO (ORCPT ); Sat, 9 Dec 2006 05:16:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S936774AbWLIKQO (ORCPT ); Sat, 9 Dec 2006 05:16:14 -0500 Received: from customer-domains.icp-qv1-irony12.iinet.net.au ([203.59.1.157]:35155 "EHLO customer-domains.icp-qv1-irony12.iinet.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936595AbWLIKQN (ORCPT ); Sat, 9 Dec 2006 05:16:13 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgAAAOobekXKoQMBdGdsb2JhbAANjTEB X-IronPort-AV: i="4.09,517,1157299200"; d="scan'208"; a="76187297:sNHT30696759" Message-ID: <457A8CEB.4080904@iinet.net.au> Date: Sat, 09 Dec 2006 21:16:11 +1100 From: Ben Nizette User-Agent: Thunderbird 1.5.0.7 (X11/20060918) MIME-Version: 1.0 To: Oliver Neukum CC: Matthias Schniedermeyer , Stefan Richter , Robert Hancock , linux-kernel , DervishD Subject: Re: single bit errors on files stored on USB-HDDs via USB2/usb_storage References: <200612081201.36789.oliver@neukum.org> <457A5384.9070806@iinet.net.au> <200612090918.26508.oliver@neukum.org> In-Reply-To: <200612090918.26508.oliver@neukum.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Oliver Neukum wrote: > Am Samstag, 9. Dezember 2006 07:11 schrieb Ben Nizette: >>>>> Also, you mentioned that the corruption occurs systematically on certain >>>>> byte patterns. Therefore it's certainly not related to the cables. >>>> It'd guess that too, but who can that say for sure. :-| >>> You may have a bit pattern that stresses the controllers and suddenly >>> a marginal cable may matter. >> The errors occur in strings of 0xFFs. From the USB standard: >> >> a “1” is represented by no change in level and a “0” is represented by a >> change in level > > Yes, plus added stuffing bits. > >> so this error-infested bytes are effectively long, quiet times on the >> wire. I would have thought this would be the _least_ stressful time for >> the controllers but maybe they are also more susceptible to noise during >> this period. > > The longer you don't change the voltage the likelier are reciever and > transmitter to get out of sync. Yes, hence the bit-stuffing, you're right :). And hence this period isn't really too stressful for the controller as the stuffed bits come relatively often. We're hoping that any wire-errors get picked up by the CRC anyway so a marginal cable under any circumstances shouldn't silently corrupt data. I love that word 'shouldn't' ;) Regards, Ben.