The HP tape drive that came with the IPX was unreliable. I bought a Sony SDT-S7000 DAT-2 drive.
The ID has to be set to 4 for device /dev/rmt/0.
The Switches have to be:
From the Sony Unix Configuration Guide v2.07:
To write files to a tape: tar cvf /dev/rmt/0 <files>
To list files on tape: tar tvf /dev/rmt/0
To get files from tape: tar xvf /dev/rmt/0