Post by Bernd-Ulrich Adrig » Sun, 21 Mar 1999 04:00:00

Quote:>How does one tell a DAT drive to use compression and/or switch
>from DDS to DDS2 or DDS3?  tar, mt, ????


Hello Tony,
First you should look at the drive, wether it has a jumper for fix setting
compression on/off/driver driven, like the HP-DAT streamers have.

The type of tape should be recognized automaticly by the device (as far as I



1. DAT Drive & DDS/DDS2/DDS3

I should jump in here since I just got my linux system talking to DAT
after a long period of poor results that led to me spending most of my
time in my other operating system.  The trick was to read all the
manpages.  You should also run the programs with the --help option to
see some of the basic uses of the program.  You should also look for
some info files.  These give a more examples than you find in the
manpages, and are very handy if you are running emacs (however, the
info directory file is not always synchronized with the files that
have been installed).  Since this is an open system, you can also look
at the source code of the programs, but the documentation should be
good enough.

There were two versions of mt in the Slackware distribution -- mt-GNU
and mt-st.  Slackware makes a symbolic link from one of these to mt.
The GNU version seemed less capable and was part of the cpio package,
while mt-st could be made to support the features used by my SONY

The tar program just builds the archives and relies on the system to
make sense of the I/O.  If you are just putting one tar file on a
tape, you may be able to use tar without mt, but anything fancy will
need mt.  Also, if you want to have several files on a tape, you need
the "non-rewinding" tape driver.

There are plans to change the way that tar finds the archive, but the
version I have still uses the TAPE environmental variable, so setting
that simplifies the mt and tar commands.

If you pop a tape in the drive and say "mt stat", you should get a
useful response giving the settings the driver is using.  If there are
any that need to be changed, there is a command to make changes, I
think it is "mt stset ..." .  I found that compression was already
set, but partitions and SCSI-2 logical blocks were not. I had gotten
in the habit of using these with the tar that I used in my other
system, so I set them.  I didn't mess with the density parameter,
since the drive seemed to be comfortable with a DDS-2 tape although it
claimed to be using DDS density.  A separate density setting for DDS-2
was known to the mt program, but my version did not mention DDS-3 (and
I wasn't that interested, since my drive doesn't know that format).

Now, you are ready to move around the tape.  If you have one with data
on it, you can try to read it.  If it is a tar, then "tar t" should
give you a good idea of whether things are working.  

Although I now feel that the tape drive is working, I am looking for
hints that would make it work better.  Further contributions to this
thread will be most welcome.
R. T. Bumby **  Rutgers Math || Amer. Math. Monthly Problems Editor 1992--1996

Telephone:    [USA] 732-445-0277 (full-time message line) FAX 732-445-5530

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