DVD-RAM writing is much slower than to be expected on my system since I upgraded to kernels newer than 2.6.7.
I have a LG GSA-4163B burner (also tested a 4120, same problem) which can write DVD-RAM at 3x, which makes 1.5x including automatic verify - about 1.9MB/s.
This is exactly what I get with a vanilla 2.6.7.
I then tried vanilla 2.6.8, 2.6.9, 2.6.10 and stock ubuntu 184.108.40.206, 2.6.9 and 2.6.10.
With all of those, writing is considerably slower: about 800 kB/s to 1 MB/s. The drive's head seems to be jumping much more than with 2.6.7.
I tried udf and ext2 filesystems (2048k block size), I checked the settings of the io-scheduler (seem to be identical).
No errors in dmesg while writing.
All tests were made with some command like
dd if=/dev/zero of=/media/dvdram/testfile bs=1024k count=4000
(well, that's huge, but values were still 25% too high with just 1G: nearly 2.5MB/s with 2.6.7, which is impossible)
I also tested writing directly to the device with dd, this seemed to be a bit faster.
The device is connected either via onboard ide (dma is on, of course) or with an external usb2 case whith which I got about 25MB/s r/w when I tested it with a HD drive.
I do not understand the changes made in the 2.6.8 kernel, and I do not even really know where to seach.
ASUS K8V SE Deluxe board, AMD64 Newcastle 3000+, (what else could be useful?)