Anyhow, I'd really like to know more about how the spanning actually works. Is it documented anywhere? http://www.amanda.org/docs and FAQ still say that the option does not exist...

Try http://wiki.zmanda.org/index.php/Splitting_dumps_across_tapes

Yes. Thanks. That's quite helpful.

A few questions still remain, though. Like

  1. Does tape splitting in any way affect the scheduling algorithm? I
     mean, what if Amanda wants to dump a certain amount in order to
     reach  the "balanced" dump size, and only much larger DLEs are
     available? Might one of those be scheduled just so that one
     "split" part can be used to fill up the remaining space?
  2. What happens to the holding disk file after a dump is partially
     written to tape? Will Amanda keep the entire file, or just what
     will be written next time around? And what if the holding disk
     data is split into "chunks"?

- Toralf