HP C6364A/C1537A Hardware Compression

[Krautkramer, John]

Hi,

I've been trying to enable hardware compression on a HP C6364A/C1537A
SCSI tape drive. Searching google and this list, I've found questions
but not any answers. I've found 'mt compression on' or 'mt
defcompression' is supposed to do this but I don't see it working. 

I'm using a DDS1 tape capable of 2G uncompressed, 4G compressed for
testing. I try turning it off with 'mt compression off' and it runs out
of tape as expected. I try the above commands and I still run out of
tape. The data I'm using as an experiment is 2.28G in total.

Any ideas? Is there a simple way to verify the compression is turned on?
The response to 'mt status' is always the same:

[root at hbwpe2 prod]# mt status
SCSI 2 tape drive:
File number=0, block number=0, partition=0.
Tape block size 0 bytes. Density code 0x13 (DDS (61000 bpi)).
Soft error count since last status=0
General status bits on (41010000):
 BOT ONLINE IM_REP_EN

Thanks in advance for any ideas!

John