On Sun, Mar 12, 2006 at 11:59:03AM -0500, stan wrote:
> I had 2 Amanda instances, one hosted on FreebSD, and the other on and
> Progeny Linux machine. I lost the root disk on the Linux server, and I'm
> building a replacement machine.
>
> Looking at the script that is run on the FreebSD machine I see that I do a
> "nt comp off" to make certain that compression is off on the tape drive,
> before I start the Amanda run.
>
> I'm building the replacement machine on an Ubuntu Linux machine, and looking
> at the man page for mt it does not seem to support this command.
>
> What are people with Linux hosts using to accomplish making certain that the
> tape drive is in uncompressed mode? I'm using an Ultrim 3 (HP) drive for
> the replacement machine, as well as (for recovery purposes) the existing
> Quantum DLT80 drive, if it matters. The DLT drive has front panel buttons
> to control this, but the U3 drive does not BTW.
While hardly a novice overall, I am a novice to tapes on linux.
Keep that in mind when reading my comments.
For the quantum, you say used only for recovery, it doesn't matter.
The drive sets itself to whatever is on the tape.
For the Ultrium 3 (lucky you, my taping sessions would take about
2 minutes on that drive :)) it actually does not hurt to leave
the compression mode on. If set to compression mode on, the
drives compression routines sense what it can and can't compress.
Anything that doesn't compress is left alone. So you can have
your cake and eat it too :) If you have some DLEs you don't
want to software compress, then the drive will help you by using
hardware compression. For your software compressed DLEs, the
drive will pass them to tape as is. So you can set your tape
size to the native 400GB (or higher if you have some uncompressed
DLEs) and still leave compression on.
If you still want control of the drives on your new linux, be aware
that different distributions handle the problem in different ways.
Some have an mt with options for setting it. Some have ways to
specify a default (??defcompression??) as well as block sizes etc.
that take place on boot. I 'think' a wave of the future is those
that use the stinit command at boot. Controlled by a stinit.def
file, it sets up 4, not 1 device name for your drive. So besides
just {n}st0, you also get {n}st0{[lma]}. In the stinit.def file
you specify what properties the driver should set each time that
particular device is opened. So I set my st0l (l for low :)
device to no compression and 32Kb blocksize and use that for
amanda. With such a fast drive you may want to experiment with
non-amanda-standard block sizes. The standard 32Kb may degrade
the drive's performance.
--
Jon H. LaBadie jon AT jgcomp DOT com
JG Computing
4455 Province Line Road (609) 252-0159
Princeton, NJ 08540-4322 (609) 683-7220 (fax)
|
