topic Re: Problem reading tar tape in Operating System - Linux

Problem reading tar tape

Andrew Kaplan — Thu, 11 Nov 2010 21:32:03 GMT

Hi there --

I created an LTO-4 tar tape on an HP-UX 11.11 risc system, and a user wanted to read the same tape on a drive that is attached to a system running the OpenSuSE 11.3 distro.

The user reports that he is unable to read the tape in question. He has confirmed that he can write to a blank LTO-4 tape as well as read from it from the OpenSUSE computer.

Does anyone have an idea as to what the cause of this issue is, and how it can be corrected?

Thanks.

Re: Problem reading tar tape

Steven Schweda — Thu, 11 Nov 2010 22:19:09 GMT

> [...] unable to [...]

Not a useful problem description. It does
not say what was tried. It does not say what
happened when it was tried. As usual,
showing actual commands with their actual
results can be more helpful than vague
descriptions and interpretations. (Or none
at all.)

> [...] issue [...]

Is that anything like a _problem_?

With only an information-free description of
the problem, it's hard to guess what the
cause might be. Within fairly broad limits,
"tar" is "tar", and "tar" on an HP-UX 11.11
system should be a proper subset of (GNU)
"tar" on any recent GNU/Linux system, but,
with my weak psychic powers, I don't know if
the tape could be read on the system where
it was written, or if the (unspecified)
destination tape drive is compatible with
the (unspecified) source tape drive, or what
might have happened to the tape in between,
or much else.

Re: Problem reading tar tape

Alan_152 — Fri, 12 Nov 2010 15:33:41 GMT

Please provide the following information:

1) the version of tar on the HPUX system
2) the version of tar on the SLES system
3) the command sequence used to write the tape
4) the command sequence used to read the tape
5) whether or not you are using the same tape drive or different drives to read/write.

Re: Problem reading tar tape

Andrew Kaplan — Fri, 12 Nov 2010 18:04:36 GMT

>>> 1) the version of tar on the HPUX system --

tar.c $Date: 2007/05/09 22:14:45 $Revision: r11.11/7 PATCH_11.11 (PHCO_36587)
$ Version_11.11 May 21 2007 14:14:14

>>> 2) the version of tar on the SLES system --

1.23

>>> 3) the command sequence used to write the tape

tar -cvf /dev/rmt/8mn .

>>> 4) the command sequence used to read the tape

I am waiting to hear back from the user...

>>> 5) whether or not you are using the same tape drive or different drives to read/write.

The drive that was used to create the tape is an HP Ultrium4-SCSI, while that to read from the tape is a Quantum LTO-4 drive.

Aside from the command sequence in item 4, is there additional information required?

Re: Problem reading tar tape

Alan_152 — Fri, 12 Nov 2010 18:12:50 GMT

You might try switching to GNU tar on the HPUX side. You have it on the SLES side, although it is an older version...

The only other thing I can think of is that one or the other (or both) of the tape drives is slightly out of alignment. They do a good job of reading tapes they wrote themselves, but not such a great job of other drives' tapes. A hardware swap might be in order to test that theory (it's actually a good idea to do that anyway if you use tapes for backup).

Re: Problem reading tar tape

Steven Schweda — Fri, 12 Nov 2010 21:16:07 GMT

> You might try switching to GNU tar on the
> HPUX side.

You might try standing on one leg and
screaming like a chicken. That should be
about as effective.

> [...] Ultrium4-SCSI [...] LTO-4 [...]

My tape drive expertise is older than these
things. Are they actually compatible (at the
density used to write the tape)? (Knowing
nothing, I'd need to read the specs, and you
may be able to do that about as well as I.)

> >>> 4) the command sequence used to read the tape
>
> I am waiting to hear back from the user...

You might try to get the actual error
message (or other behavior), too.

> [...] is there additional information
> required?

More than none, you mean? I assume that
it's too late to find out, but it would be
nice to know if the tape could be read on
the drive where it was written.

Re: Problem reading tar tape

Steven Schweda — Fri, 12 Nov 2010 22:44:02 GMT

> [...] Ultrium4-SCSI [...] LTO-4 [...]

As I read the Google search results,
"Ultrium4" might actually be "LTO-4 Ultrium",
which would seem to be approximately equal to
plain-old "LTO-4".

This might all be clearer with accurate
information instead of made-up names.