On Monday 23 September 2002 13:02, Mike Brodbelt wrote:
>Hi all,
>
>I've recently upgraded my amanda server. The machine was a
> Pentium-II 350, and was running with hardware compression, but is
> now a dual processor Athlon 2000+, so I've switched it over to
> software compression. The tape drive is a Quantum DLT drive, and
> I'm wondering how to turn of compression on the tapes.
>
>Having read all about dd'ing zeros to the start of the tape, and
>rewriting the label, I was preparing myself for trouble, but the
> tape drive seems to be OK to just turn compression off with mt:-
>
># mt -f /dev/nst0 datcompression
>Compression off.
>Compression capable.
>Decompression capable.
>
>I turned compression off, and loaded a new tape (which has
> previously been written compressed). The compression setting
> remained off according to mt, and the transfer rate to tape has
> been about 4700 - 4800 KB/s for large filesystems. Is that it?

Its possible that your DLT drive doesn't record the compression 
status to the tape, but that hardly makes sense to.

All our grousing about this is because the status on the tape 
vis-a-vis compression is recorded in a header thats part of the 
Tape Recognition System in DAT tape drives.  In such a drive, you 
can turn it off, and the instant it sees this flag during the the 
tape acceptance phase where its running the tape back and forth 
over the first couple of feet of the tape when you put a tape into 
the drive, it will turn it back on regardless of the dip switch 
setting.

The main reason its so hard to handle in an amanda environment is 
that amanda causes a read of this TRS identification block after 
changing the tape by herself, giving the user no chance to access 
the drive and turn it back off.  Hence the shennigans by hand, or a 
short script if you have a bunch of them to do.  Other drives may 
not have this hidden header, which means they won't suffer from 
this "I'm smarter than you" syndrome.

> I'd believe it, but all the messages about turning compression
> off being problematic have left me wondering whether it's really
> off....
>
>Secondly, as my filesystems have grown, my reports have become
> less tidy - the columns of figures are running together. Is there
> an easy way to tell amanda to space the columns on reports out a
> bit more??
>
Thats adjustable in amanda.conf, but currently commented
 out by default.

-- 
Cheers, Gene
AMD K6-III@500mhz 320M
Athlon1600XP@1400mhz  512M
99.16% setiathome rank, not too shabby for a WV hillbilly