Subject: HP 1533A DAT drive & Compression
To: Current-Users@Netbsd. Org <email@example.com>
From: Bill Dorsey <firstname.lastname@example.org>
Date: 10/01/2000 00:10:23
I was wondering if anyone has successfully used an HP 1533A
DAT drive with compression turned on. I've filled a 4 gig
tape 5 times today and every time NetBSD reports the tape is
full at the 4 gig point. I'm using a 4-gig native capacity
DDS-2 tape (should give up to 8 gig compressed capacity).
I'd hope to get better than 1:1 compression on my ufs filesystem.
I tried setting the DIP switches on the HP drive to force
compression on. I tried various recommended switch settings
from HPs web site (which contains very spotty information on
this drive -- shame on HP) for various operating systems
including Sun 4.x, SGI, generic PC, and DEC. I also tried
messing with the NetBSD mt command. If I have the compression
hard-wired on, mt compress 1 fails, but mt compress 0 succeeds.
If I have the switches set to allow the computer to select
compression, then mt compress 1 succeeds. When I do an mt
status after the mt compress, it always comes back with the
same thing (and reports the density is 36 -- DDS-2).
If anyone has any suggestions for other things to try, I'd love
to hear about them. It would be nice if there were a simple
way to determine whether compression was working or not without
filling a tape (I will use 1.3 gig tapes from now in in my
experiments until I get this working).
BTW, the hardware is a DEC PWS 433a (Alpha) running NetBSD 1.4Y.
Bill Dorsey "The unarmed man is not just defenseless --
email@example.com he is also contemptible." Machiavelli