-R[W] for Linux

by <appro@fy.chalmers.se>, September 2006

Q. What is this page (not) about?

A. Maybe to your disappointment it is not about video^(*). The scope of this page is primarily computer storage applications of Blu-ray Disc and DVD±RW/±R, things like backup, archiving, data exchange... The downloadable files are an optional Linux 2.4 kernel DVD+RW patch and a couple of user-land utilities dubbed as dvd+rw-tools.

^(*) Though it doesn't mean that you can't burn DVD-Video discs with dvd+rw-tools. [Unlike Video-CD] DVD-Video is "molded" in an ordinary data file system and therefore no explicit support by the burning program is actually required. In other words it is the DVD-Video content preparation which is beyond the scope of this page.

Q. Kernel patch? This sounds too complicated already! Can't I just use [vanilla] cdrecord?

A. It should be explicitly noted that the user-land utilities, dvd+rw-tools, do suffice for BD/DVD recording without explicit kernel support. So if they fulfill your requirements, then patching the kernel is by all means optional. As for [vanilla] cdrecord, non-CD recording strategies are somewhat different, so it simply doesn't work (nor does dvdrecord with media other than DVD-R[W], despite what RedHat 7.3 Release Notes say). On additional note Linux kernel version 2.6>=10 is equipped with packet writing driver which supports even DVD rewritable media, but I haven't tested it myself, so don't ask:-)

Q.	Kernel patch? This sounds too complicated already! Can't I just use [vanilla] cdrecord?
A.	It should be explicitly noted that the user-land utilities, dvd+rw-tools, do suffice for BD/DVD recording without explicit kernel support. So if they fulfill your requirements, then patching the kernel is by all means optional. As for [vanilla] cdrecord, non-CD recording strategies are somewhat different, so it simply doesn't work (nor does dvdrecord with media other than DVD-R[W], despite what RedHat 7.3 Release Notes say). On additional note Linux kernel version 2.6>=10 is equipped with packet writing driver which supports even DVD rewritable media, but I haven't tested it myself, so don't ask:-)

Q. What is the kernel patch good for then?

A. DVD+RW (but not DVD+R nor any DVD-dash) is a true random write access media and therefore is suitable for housing of an arbitrary file system, e.g. udf, vfat, ext2, etc. This, and this alone, qualifies DVD+RW support for kernel implementation. However, I have to recommend to deploy it with caution, see tutorial for further details. Also note that not all OEMs seem to live up to the promise of true random write access. As for the moment of this writing apparenly only 2nd generation Ricoh-based units (see dvdplusrw.org for generation listings) equipped with later firmware can sustain I/O fragmentation (see Technical Ramblings below for further details) and perform reliably.

Q.	What is the kernel patch good for then?
A.	DVD+RW (but not DVD+R nor any DVD-dash) is a true random write access media and therefore is suitable for housing of an arbitrary file system, e.g. udf, vfat, ext2, etc. This, and this alone, qualifies DVD+RW support for kernel implementation. However, I have to recommend to deploy it with caution, see tutorial for further details. Also note that not all OEMs seem to live up to the promise of true random write access. As for the moment of this writing apparenly only 2nd generation Ricoh-based units (see dvdplusrw.org for generation listings) equipped with later firmware can sustain I/O fragmentation (see Technical Ramblings below for further details) and perform reliably.

Q. What are the dvd+rw-tools for?

A. As implied/already mentioned - to master the Blu-ray Disc and DVD media, both +RW/+R and -R[W]. I could simply refer to the tutorial below, but figured that couple of words about the [original] design ideas behind growisofs, the principal burning utility, wouldn't harm. Even though a modified kernel can let you put for example an ext2 file system on DVD+RW, it's probably not very practical, because you most likely want to access the data on an arbitrary computer. Or in other words you most likely want ISO9660. The trouble is that you might as well want to add data now and then. And what options do you have in the lack of multiple sessions (no, DVD+RW has no notion of multiple sessions)? Complete re-mastering which takes more and more time as data set grows? Well, yes, unless you employ growisofs! Growisofs provides the way to both lay down and grow an ISO9660 file system on (as well as to burn an arbitrary pre-mastered image to) all supported optical media.

Q.	What are the dvd+rw-tools for?
A.	As implied/already mentioned - to master the Blu-ray Disc and DVD media, both +RW/+R and -R[W]. I could simply refer to the tutorial below, but figured that couple of words about the [original] design ideas behind growisofs, the principal burning utility, wouldn't harm. Even though a modified kernel can let you put for example an ext2 file system on DVD+RW, it's probably not very practical, because you most likely want to access the data on an arbitrary computer. Or in other words you most likely want ISO9660. The trouble is that you might as well want to add data now and then. And what options do you have in the lack of multiple sessions (no, DVD+RW has no notion of multiple sessions)? Complete re-mastering which takes more and more time as data set grows? Well, yes, unless you employ growisofs! Growisofs provides the way to both lay down and grow an ISO9660 file system on (as well as to burn an arbitrary pre-mastered image to) all supported optical media.

Q. But if they support both + and - recording strategies, why are they called dvd+rw-tools?

A. For historical/nostalgical reasons, as originally they did support exclusively DVD+plus. On the other hand now, when the vast majority of DVD burners that are being introduced to the market today are DVD+capable, the name most likely refers to your unit in either case. And you can always consider the plus in the name as notion of a unique quality, such as "seamless" multisessioning, not as reference to some particular format:-)

Q.	But if they support both + and - recording strategies, why are they called dvd+rw-tools?
A.	For historical/nostalgical reasons, as originally they did support exclusively DVD+plus. On the other hand now, when the vast majority of DVD burners that are being introduced to the market today are DVD+capable, the name most likely refers to your unit in either case. And you can always consider the plus in the name as notion of a unique quality, such as "seamless" multisessioning, not as reference to some particular format:-)

Q. Do I still need cdrtools?

A. Yes. It should be explicitly