为什么在ubuntu下使用packet-writing功能，刻录速度很慢？

Hi ALL：
在linux内核../Documentation/cdrom/packet-writing.txt中这样写到：
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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:
# dvd+rw-format /dev/hdc (only needed if the disc has never been formatted) # 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.
# dvd+rw-format /dev/hdc
# pktsetup dev_name /dev/hdc
# mkudffs /dev/pktcdvd/dev_name
# mount /dev/pktcdvd/dev_name /cdrom -t udf -o rw,noatime
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也就是说用户支持将UDF文件系统盘mount后，在应用层可以像操作硬盘的方式来操作光盘。比如正常的open，write功能。
我按照上面所描述的两种方式都能过成功刻录文件，但是在刻录时发现刻录速度很慢，linux下4XDVD盘实际刻录速度在0.8X左右；但是在Window系统下，相同格式的同一种盘实际刻录速度却能达到3X左右。
不知道大家在Linux系统下，有没有人在使用packet-writing功能时碰到相似的问题？有什么好的办法解决？