From: Peter Osterlund <petero2@telia.com> Added information about packet writing for DVD+RW and DVD-RW media. Signed-off-by: Peter Osterlund <petero2@telia.com> DESC Trivial CDRW packet writing doc update EDESC From: Peter Osterlund <petero2@telia.com> Document that pktcdvd block devices have a 2KB block size. Signed-off-by: Peter Osterlund <petero2@telia.com> Signed-off-by: Andrew Morton <akpm@osdl.org> --- 25-akpm/Documentation/cdrom/packet-writing.txt | 66 +++++++++++++++++++++++++ 1 files changed, 66 insertions(+) diff -puN Documentation/cdrom/packet-writing.txt~packet-writing-docco Documentation/cdrom/packet-writing.txt --- 25/Documentation/cdrom/packet-writing.txt~packet-writing-docco Mon Aug 16 16:10:13 2004 +++ 25-akpm/Documentation/cdrom/packet-writing.txt Mon Aug 16 16:10:18 2004 @@ -20,3 +20,69 @@ Getting started quick - Now you can mount /dev/pktcdvd0 and copy files to it. Enjoy! # mount /dev/pktcdvd0 /cdrom -t udf -o rw,noatime + + +Packet writing for DVD-RW media +------------------------------- + +DVD-RW discs can be written to much like CD-RW discs if they are in +the so called "restricted overwrite" mode. To put a disc in restricted +overwrite mode, run: + + # dvd+rw-format /dev/hdc + +You can then use the disc the same way you would use a CD-RW disc: + + # pktsetup /dev/pktcdvd0 /dev/hdc + # mount /dev/pktcdvd0 /cdrom -t udf -o rw,noatime + + +Packet writing for DVD+RW media +------------------------------- + +According to the DVD+RW specification, a drive supporting DVD+RW discs +shall implement "true random writes with 2KB granularity", which means +that it should be possible to put any filesystem with a block size >= +2KB on such a disc. For example, it should be possible to do: + + # mkudffs /dev/hdc + # mount /dev/hdc /cdrom -t udf -o rw,noatime + +However, some drives don't follow the specification and expect the +host to perform aligned writes at 32KB boundaries. Other drives do +follow the specification, but suffer bad performance problems if the +writes are not 32KB aligned. + +Both problems can be solved by using the pktcdvd driver, which always +generates aligned writes. + + # pktsetup /dev/pktcdvd0 /dev/hdc + # mkudffs /dev/pktcdvd0 + # mount /dev/pktcdvd0 /cdrom -t udf -o rw,noatime + + +Notes +----- + +- CD-RW media can usually not be overwritten more than about 1000 + times, so to avoid unnecessary wear on the media, you should always + use the noatime mount option. + +- Defect management (ie automatic remapping of bad sectors) has not + been implemented yet, so you are likely to get at least some + filesystem corruption if the disc wears out. + +- Since the pktcdvd driver makes the disc appear as a regular block + device with a 2KB block size, you can put any filesystem you like on + the disc. For example, run: + + # /sbin/mke2fs /dev/pktcdvd0 + + to create an ext2 filesystem on the disc. + + +Links +----- + +See http://fy.chalmers.se/~appro/linux/DVD+RW/ for more information +about DVD writing. _