Travan SCSI tape random failures

[Trevor Blackwell]

I'm running 4.7-RELEASE on a dual P4-Xeon machine and trying to back up
to a Seagate 10/20 GB Travan tape drive:

sa0 at ahd1 bus 0 target 4 lun 0
sa0: <Seagate STT20000N 6A51> Removable Sequential Access SCSI-2 device 
sa0: 10.000MB/s transfers (10.000MHz, offset 15)

It's in the default mode:

tlb tlb$ sudo mt -f /dev/sa0.ctl status
Mode      Density              Blocksize      bpi      Compression
Current:  0x47                 variable       0        disabled
...

When I write to it, it usually fails after a few hundred MB, but the
amount of data is not repeatable even when I write identical files. For
example:

tlb tlb$ sudo dd of=/dev/nsa0 if=[huge file] bs=10240
dd: /dev/nsa0: short write on tape device
18139+0 records in
18138+1 records out

The kernel reports:

/kernel: (sa0:ahd1:0:4:0): WRITE FILEMARKS. CDB: 10 0 0 0 1 0 
/kernel: (sa0:ahd1:0:4:0): MEDIUM ERROR info:1 asc:c,0
/kernel: (sa0:ahd1:0:4:0): Write error
/kernel: (sa0:ahd1:0:4:0): failed to write terminating filemark(s)
/kernel: (sa0:ahd1:0:4:0): tape is now frozen- use an OFFLINE, REWIND or
MTEOM command to clear this state.

The drive and tape are both new; I haven't used this kind before. Any
suggestions?

-- 
Trevor Blackwell      tlb at anybots.com       (650) 210-9272