> To summarize : using a stock kernel allows the use of /dev/hdx with > dvd+rw-tools. Patching the kernel allows for true direct access to dvd+r(w) > discs, but needs ide-scsi on 2.4.x kernels (the stock 2.6.0 kernel > already has the relevant "patch"). > > Three questions : > > 1) Is the above summary correct ?
Not really. The very last assumption, namely "(the stock 2.6.0 kernel already has the relevant "patch")," is wrong. User-land burning applications, such as dvd+rw-tools, are currently the only way to perform DVD recordings under 2.6. In other words there is no kernel DVD+RW support for 2.6 yet (there is an explicit statement about this on dvd+rw-tools page). > 2) Is the 2.4 kernel patch compatible with the "packet writing" patch one > can use to allow packet writing to CD, thus allowing to create and update > R/W UDF filesystems (à la Adaptec DirectCD) ? No, but there was work done in this direction, see http://lists.debian.org/cdwrite/2003/cdwrite-200309/msg00061.html. See also "Packet writing on NEC1300" thread at http://lists.debian.org/cdwrite/2003/cdwrite-200309/threads.html for background discussion. > (The very same question may > or may not be relevant for 2.6 kernels). Answer for now is "no, period." > 3) [ Out of my deep ignorance of DVD[+|-]R(W) standards ] : Is it possible > to create such UDF R/W filesystems on DVDs ? Yes (for DVD+RW), but consensus is that Linux UDF implementation is too inefficient to be useful. To my knowledge most people who tried it, adandoned it in favor of other solutions: growisofs -M or pre-mastering a file system image in loopback mounted 4.38GB container and burning it with growisofs -Z /dev/dvd=container. > This could allow for a swell > incremental backup system for small/medium systems ... As I understand it, > growisofs currently allows for something like that (i.e. one can, for > example, *add* an incremental tar archive to a disk already containing a > tar archive). Depends on what do you mean by "contain a tar archive." If you mean "an isofs volume with tar archive," then yes, growisofs takes care of it(*). But if you mean that media is tar-formatted, e.g. "tar cf - /some/dir | growisofs -Z /dev/dvd=/dev/fd/0," then only next version will provide for appending other tar archives (but you'll have a lot of calculations to perform yourself!). (*) with reservations for isofs implementation deficiencies, such as 2GB-1 file size limit, discussed multiple time on the list; > The current "packet writing" tools allow for *replacing* an > existing file on a CD. Is such a solution possible on a DVD ? As already mentioned above, yes, but it's impractical. A.