I had so many problems using DVD-RAM on Linux. I formatted them as ext2 and mounted the device /dev/sr0 directly, and wondered why there were so many SCSI-errors. I retried formatting as UDF, but this wasn’t better either. With UDF, the writing process didn’t even finish overnight!
I finally found out what the problem was: I should have used Packet Writing. With this, and together with UDF and certain mount options, it finally worked, thanks to a (German) Linux DVD-RAM HOWTO.
In short: Load the pktcdvd kernel module (or compile support into your kernel). Then issue the pktsetup command as told in the HOWTO (or have a corresponding init-script do it). Format (or keep, if you just bought it) your DVD-RAM as UDF; the UDF revision is only important if you want to share the disk with old operating systems (such as Win2k). Then mount your disk using the options rw,noatime,async,users. I had to switch from kernel 2.6.15 to 2.6.17, as otherwise I got a
pktcdvd: Wrong disc profile (0)
error in the syslog. With 2.6.15, it only worked mounting read-only, and remounting (
-o remount,rw) as read-write.