I was thinking of trying to do backups to CD-R, and wondered if anyone else
has already done something like this.  What I am considering doing is
fiddling with dump to give it an easy way to communicate with cdrecord
(though maybe I can just use a fake RMT server, so perhaps dump needs no
work at all (other than, perhaps, to give it a "density" flag that sets
things appropriately for the size of a CD...)).  (This assumes that the
"experimental" packet-writing mode of cdrecord actually works, of course.)

Why CD-R, as opposed to (for example) tape?  I have a TR4 tape drive, but
the tape drive is slow and noisy, and the tapes are unreliable and expensive.
CD-R media is cheap (even CD-RW is now cheap) and reliable, and the
drive is silent and, well, OK, it's slow, but not quite as slow as the
tape drive.  The disadvantage, of course, is having to constantly feed
media to the drive during a backup; I've carefully partitioned my disk
drives so that every partition fits on one TR4 tape...