When using a disk-based 'virtual tape changer', is there is any point in using a holding disk? I understand that a holding disk is a good idea
when using real tapes, as this helps in keeping the tape drive streaming -- that is the holding disk smooths out the 'bumps' in the actual
backup process.
AFAIK, when writing directly to tape - even virtual tape - only one client can be dumped simultaneously. When dumping to holding disks,
several dumps can run in parallel.

I only have *one* client (the server IS the client). (I know, Amanda might be considered overkill in this case, but Amanda does all sorts of things in terms of managing backups, etc.) Simultaneous dumping of multiple DLE from a single client is possible.

But probably not advisable if all of the DLEs are on a single spindle.

If something happens to the backup device, dumps could still be collected on, and recovered from, the holding disk.

I suppose.