No, the operator control panel has a status menu where you can show the drive parameters, compression is ON.

I have tried this:

http://wiki.zmanda.com/index.php/Hardware_compression

And sent the mt command to the drive. but it seems to reset to HW compression while reusing a tape. It looks like when it read the tape header, it sees that the tape was written with HW compression and resets itself.

My tapes are already labeled, I could probably just rewrite the label with HW compression OFF (The wiki could be a bit cleared about that, what does " Re-write the label block and write more /dev/zero blocks to flush its buffers" exactly mean, won't it overwrite the stuff AFTER the label (the Backups that is), but considering that it does not hurt to leav it on, I'll keep it that way.

Thanks