I am using a Travan 20/40GB tape on a PV100T tape driver into my DELL 
poweredge SC1420 machine runing with NetBSD 2.0.

Very often, when I want to rewind my tape, I am getting the following 
message : netbsd: st0: WARNING: cannot revert to default density

Hereafter is the result of a mt status

SCSI tape drive, residual=0
ds=3
er=0
blocksize: 1024 (0, 0, 0, 0)
density: 0 (0, 0, 0, 0)
current file number: 0
current block number: 0

Up to now, I have not been able to make a backup copy on the tape.

Can anyone tell me what should be the default density param for my config ?

Any experince with this tape driver on similar config ?

Any further advice re the backup using star would be appreciated.

Regards