Quantum DLT4000 on 4.5-R: "Device busy"

[Luke Lussier]

Greetings,

(Apologies in advance if this is not the correct list for this question)

I am attemping to get a new tape drive (Quantum DLT4000, external) working
on my FreeBSD (4.5-R, i386) machine. The kernel detects the drive during
boot:

ahc0: <Adaptec 2940 Ultra SCSI adapter> port 0xdc00-0xdcff mem
	0xe7003000-0xe7003fff irq 11 at device 13.0 on pci0
aic7880: Ultra Wide Channel A, SCSI Id=7, 16/255 SCBs
sa0 at ahc0 bus 0 target 4 lun 0
sa0: <Quantum DLT4000 DA97> Removable Sequential Access SCSI-2 device
sa0: 10.000MB/s transfers (10.000MHz, offset 15)

However, when trying to interact with the /dev/sa0 device via mt and tar
commands, the device is reported to be busy:

[root at th]:/dev $ mt status
mt: /dev/nsa0: Device busy
('mt offline' fails with the same message, as well)

I have tried resetting the drive, changing SCSI IDs, rebooting, reseating
the tape cartridge, to no avail. The tape drive works under a
Solaris/Sparc 8 machine, so I do not believe the drive or cable are at
fault.

I am unfamiliar with tape drives in general under BSD. Am I doing
something wrong?

-Luke