Very Computer

I have a 4mm 90m DAT tape written from a machine running
HPUX10.20 (created with `/usr/bin/tar cvf /dev/rmt/0m DIR').
To my dismay, I can't seem to read it from my Linux
Slackware-1.2.13 system.  The SCSI DAT drive on my Linux box
might be a Toshiba -- I don't remember and can't look now.
The face of the DAT drive on the HP box says `HP6400 2000 DC'.

I tried the command
  tar xvf /dev/nst0
where tar is GNU tar 1.11.14.

I can make tapes on my linux box and read them with the above,
but get errors right away when trying to read the HP-written tapes.
Right now I'm going to try to write a tape on the HP using GNU tar
rather than the /usr/bin one.  But I think that was the first thing
I tried about a year ago (different HPUX release) when I had the
same problem -- I never managed to read the HP-written tape back
then.

If anyone can give me advice on this, I'd appreciate it.

Jim

: I have a 4mm 90m DAT tape written from a machine running
: HPUX10.20 (created with `/usr/bin/tar cvf /dev/rmt/0m DIR').
: To my dismay, I can't seem to read it from my Linux
: Slackware-1.2.13 system.  The SCSI DAT drive on my Linux box
: might be a Toshiba -- I don't remember and can't look now.

Hmmm, never seen a Toshiba DAT drive - try a
cat /proc/scsi/devices (devices could be wrong, but the file name should be
similar) or have a look in the system startup log in /var/log/messages on
your Linux box. Maybe it's a Sony DAT ...

: The face of the DAT drive on the HP box says `HP6400 2000 DC'.

: I tried the command
:   tar xvf /dev/nst0
: where tar is GNU tar 1.11.14.

: I can make tapes on my linux box and read them with the above,
: but get errors right away when trying to read the HP-written tapes.
: Right now I'm going to try to write a tape on the HP using GNU tar
: rather than the /usr/bin one.  But I think that was the first thing
: I tried about a year ago (different HPUX release) when I had the
: same problem -- I never managed to read the HP-written tape back
: then.

The DAT drive on your HP probably writes in compressed mode by default.
DAT tapes written with compression enabled on hp drives are _not_ compatible
with non-HP DAT drives ! Try setting the DAT drive to no compression
(take a look at the mt man page, I _think_ it's in there, I don't have a
HP 9000 to look at here, sorry).

Hope this helps,
regards,

   Date: 26 Mar 1997 15:31:40 GMT

   : I can make tapes on my linux box and read them with the above,
   : but get errors right away when trying to read the HP-written tapes.
   : Right now I'm going to try to write a tape on the HP using GNU tar
   : rather than the /usr/bin one.  But I think that was the first thing
   : I tried about a year ago (different HPUX release) when I had the
   : same problem -- I never managed to read the HP-written tape back
   : then.

   The DAT drive on your HP probably writes in compressed mode by default.
   DAT tapes written with compression enabled on hp drives are _not_ compatible
   with non-HP DAT drives ! Try setting the DAT drive to no compression
   (take a look at the mt man page, I _think_ it's in there, I don't have a
   HP 9000 to look at here, sorry).

HP-UX controls the compression mode by using different devices.
"/dev/rmt/0m" doesn't follow the standard HP-UX device-naming
convention, so I can't tell whether it is likely to be compressed or
not.  For example, here are some typical devices (from "/dev/rmt/")
from our HP-UX 10.10 machine:

crw-rw-rw-   2 bin      bin      205 0x041000 Aug 27  1996 c4t1d0BEST
crw-rw-rw-   2 bin      bin      205 0x041080 Aug 27  1996 c4t1d0BESTb
crw-rw-rw-   2 bin      bin      205 0x041040 Aug 27  1996 c4t1d0BESTn
crw-------   2 root     sys      205 0x0410c0 Aug 27  1996 c4t1d0BESTnb
crw-rw-rw-   1 bin      bin      205 0x0410c1 Jan 31 16:16 c4t1d0DDS1nb

The first four devices all use compression; the last one does not.
The difference is that the LSB of the device minor word is set to
disable compression.

I don't remember all of the details, but they are documented in one of
the HP-UX manuals.

/dev/rmt/0m  - Read ANY tape, Write UNCOMPRESSED tapes
/dev/rmt/3hc - Read/Write with Full Compression

The above are the "rewinding" tape devices.  To use the non-rewinding
equivalents under HP-UX, use /dev/rmt/0mn, etc.

Hope that helps!

--
 --
/-------------------------------------------\

\-------------------------------------------/

  This article was originally posted on Date: 2 Apr 1997 12:46:58 GMT
Because it was apparently not received at (m)any sites, I am reposting
it below. In order to try to prevent clutter, I have cancelled the old
article.

[deleted]

Quote:> HP-UX controls the compression mode by using different devices.
> "/dev/rmt/0m" doesn't follow the standard HP-UX device-naming
> convention, so I can't tell whether it is likely to be compressed or
> not.  For example, here are some typical devices (from "/dev/rmt/")
> from our HP-UX 10.10 machine:

> crw-rw-rw-   2 bin      bin      205 0x041000 Aug 27  1996 c4t1d0BEST
> crw-rw-rw-   2 bin      bin      205 0x041080 Aug 27  1996 c4t1d0BESTb
> crw-rw-rw-   2 bin      bin      205 0x041040 Aug 27  1996 c4t1d0BESTn
> crw-------   2 root     sys      205 0x0410c0 Aug 27  1996 c4t1d0BESTnb
> crw-rw-rw-   1 bin      bin      205 0x0410c1 Jan 31 16:16 c4t1d0DDS1nb

> The first four devices all use compression; the last one does not.
> The difference is that the LSB of the device minor word is set to
> disable compression.

Quote:> I don't remember all of the details, but they are documented in one of
> the HP-UX manuals.