On 9 Jun 2002, ulrich mensfeld wrote:
Hallo Peter Osterlund ,
Yes, the pktcdvd module makes the cdrw look like a normal block device, so it should be possible to put any filesystem on top of it. The only potential problem is that the block size used by the file system must be supported by the block device. This is what I used for the test:
pktsetup /dev/pktcdvd0 /dev/scd0 /sbin/mke2fs -b 2048 /dev/pktcdvd0
Here i get allways the error:
Input/output error while trying to determine filesystem size
What could that be? i deleted the cdrw prior to this try with cdrecord blank=fast speed=4, and it is a 700MB CDRW.
The disc must be formatted for packet writing with cdrwtool before you can put a filesystem on it. If you already have a disc with a udf filesystem, try the mke2fs command without blanking the disc first. (If you later want to go back to the udf filesystem, just use the mkudf program. There is no need for a full reformat.)
Speed-issues: Yesterday i made another try with udf, on a fresh 700MB 4x CDRW. Copying the kerneltree with cp -a /usr/src/linux /mnt/cdwriter needs about 80 minutes for about 150MB! (and as estimated, there were corrupted files again on the cd)
I think the speed issue is caused by two things: The udf filesystem seems to be inefficient at handling many small files. I don't know if that's caused by the current implementation or by something in the udf specification that requires such behaviour. The pktcdvd module is bypassing the the I/O elevator when creating write requests for the CDRW drive. This can make performance really suffer when there is a mixed read/write load. The 2.5 version of pktcdvd has fixed this problem, but a backport is not easy because it relies heavily on the new bio infrastructure in 2.5. -- Peter Osterlund - petero2@telia.com http://w1.894.telia.com/~u89404340