FreeBSD/UNIX backups to DVD+RW

[James Riendeau]

I'm trying to setup backups to the DVD-RW drive on our new server before it
goes into production.  I've got the DVD-RW drive working, and I figured out
how to dump to it:

# dvd+rw-format /dev/cd0
# dump -0 -uL -C16 -B4589840 -P 'growisofs -speed=4 -Z /dev/cd0=/dev/fd/0'
/usr

A test restore comes out clean:

# restore -Nxvb /dev/cd0

The problem is most of the partitions are tiny (< 1G) and I would like to
fit more then one partition on each DVD.  I figured just passing -M (append
data) instead of -Z (new session) would do it:

# dump -0 -uL -C16 -a -P 'growisofs -speed=4 -M /dev/cd0=/dev/fd/0' /home

But growisofs fails with :-( /dev/cd0 doesn't look like isofs..., and of
course dump fails with "Broken pipe".

Any clues to how to get this to work?  (Webpage link is sufficient if there
is something out there.  I couldn't find one.)

I'm fairly new to the FreeBSD/UNIX world, so please be gentle.

Thanks,

-james