From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932431AbWB1TOe (ORCPT ); Tue, 28 Feb 2006 14:14:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932435AbWB1TOe (ORCPT ); Tue, 28 Feb 2006 14:14:34 -0500 Received: from linux01.gwdg.de ([134.76.13.21]:6602 "EHLO linux01.gwdg.de") by vger.kernel.org with ESMTP id S932432AbWB1TOd (ORCPT ); Tue, 28 Feb 2006 14:14:33 -0500 Date: Tue, 28 Feb 2006 20:14:12 +0100 (MET) From: Jan Engelhardt To: Phillip Susi cc: Sam Vilain , Luke-Jr , Jesper Juhl , Bernhard Rosenkraenzer , linux-kernel@vger.kernel.org Subject: Re: [slightly OT] dvdrecord 0.3.1 -- and yes, dev=/dev/cdrom works ;) In-Reply-To: <44049D5A.1010806@cfl.rr.com> Message-ID: References: <200602250042.51677.bero@arklinux.org> <200602261330.15709.luke@dashjr.org> <9a8748490602260529h3a2890bhce4112feefb7cb1f@mail.gmail.com> <200602261339.13821.luke@dashjr.org> <440240F8.3010207@vilain.net <44049D5A.1010806@cfl.rr.com> 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 >> Yes. A 650 MB *CD*-RW (DVD-RW too?) formatted in packet mode only has like >> 500-something megabytes to allow for the sort of seeks required. >> On DVD+RW, you get the full 4.3 GB (4.7 gB) AFAICS. > > DVD-RAM physically is formatted like a hard disk. It is broken up into zones > that hold different numbers of sectors which are individually and randomly > read/writable. CD/DVD+-RW media is organized as a single long groove that > consists of an unbroken series of large blocks composed of small blocks with > user and control data interleaved and error corrected. It is for this reason > that historically it could only be recorded from start to finish in one pass. > > There are two modern techniques to allow pseudo random write access for all > forms of CD/DVD +/- RW media. These are packet mode, and mount rainier mode. > MRW mode formats the disk into 32 KB blocks made up of 2048 byte sectors which > are individually writable as far as the OS knows, because an MRW compliant > drive is required to internally handle any required read/modify/write cycles to > update the 32 KB blocks. MRW mode also reserves some of the disk for sector > sparing which the drive firmware also handles. MRW mode is typically used on > dvd+rw media. IIRC, this format typically "wastes" about 10% of the capacity of > the medium. > I doubt that. 10% of a 4.3 GB disk are, well, roughly 430 MB, which would make df show 3.9 GB as mountpoint size, not 4.3 GB. [MB and GB are powers of 1024 here.] Jan Engelhardt --