HP VS80, no hw compression w/ linux dump

[Jyrki Setälä]

Hi,

I have a problem with internal HP VS80 tape drive. For some reason hardware compression doesn't work. I've only tested this with dump, but as far as I know, hardware compression is hardware compression indipendent of the tool you use.

I've tested with two tapes: HP 40/80 C5141F and MAXELL DLT IV 40-80GB, both should be compatible with the drive. Although I can store only 40GB on both tapes when dump receives end of media.

I run dump as:
dump -0 -a -f /dev/st0 /path_to_files

I've thested the hp_ltt tools to check the hardware compression. Here's the result:
- Test 'Test Script' started on device 'HP DLT VS80' at address
'20.6.0[2-/dev/sg2]'
- Passed
- Operations Log
- Executing Rules Based Analysis (rules file is /tmp/LTT_T6BjMV8.tst)
- Checking for a tape...
- Checking for a write-protected cartridge...
- Rewinding the tape...
- Writing 600MB of data...
- Rewinding the tape...
- Reading 600MB of data...
- Rewinding the tape...
- Test passed
- Analysis Results
- Compression test
- Testing the DLT VS80
- Compressed write transfer rate = 3 Mb/sec (I/O path, not backup data
rate)
- Compressed read transfer rate = 3 Mb/sec (I/O path, not backup data
- Compressed read transfer rate = 3 Mb/sec (I/O path, not backup data
rate)
- Read compression ratio is: 2.27:1
- Write compression ratio is: 2.27:1

To me this sounds like it works, but then again I can't write more than 40GB on the tape.

Background of the system:
Distribution: Red Hat Enterprise Linux WS release 3 (Taroon Update 4)
Kernel: 2.4.21-27.0.1.EL
Dump version: 0.4b28-7
SCSI card chipset: sym53c896

Any help/pointers greatly appreciated.

Regards,
Jyrki Setäl