[ip6ix]

Many thanks to everyone who responded.

Shunt looks quite interesting, I'll take a look at that more closely later, thanks jggimi.

Since the size of the backup is relatively small (and consists mainly of text), the compression ratio is good. With compression this will easily fit on one disk. I might add par2 verification using par2cmdline also, this seems like a good idea for important data (though I tend to make more than one backup at a time, so may be overkill).

I wanted to create a UDF filesystem on the dvd-ram disk, as this would be a very convenient way of accessing the dvd for backup purposes, but it seems this is not (yet?) available in OpenBSD. I can mount an already formatted udf volume using mount_udf(8), but it's read-only.