I have scsi LTO3 tape attached / OpenSUSE 11.1

what happens:

linux:~ # dd if=/dev/zero of=dummy_file bs=1M count=5
5+0 records in
5+0 records out
5242880 bytes (5.2 MB) copied, 0.132575 s, 39.5 MB/s

linux:~ # mt -f /dev/nst0 tell
At block 0.
linux:~ # tar cvzf /dev/nst0 dummy_file
dummy_file
linux:~ # mt rewind
linux:~ # mt tell
At block 0.

linux:~ # tar tvzf /dev/nst0

gzip: stdin: not in gzip format
tar: Child returned status 1
tar: Error exit delayed from previous errors
linux:~ #

But...
linux:~ # tar cvzf - dummy_file | cat > /dev/nst0
dummy_file
linux:~ # mt tell
At block 3.
linux:~ # mt rewind
linux:~ # tar tvzf /dev/nst0
-rw-r--r-- root/root 5242880 2009-11-03 02:29 dummy_file
linux:~ #

So, if I put it trough pipe it is working, otherwise not.
Anybody seen something like this?

I think that 'tar' creates the archive first, and then gzips it. It is thus unable to gzip the archive created on the tape.

What happens if you try 'tar tvf /dev/nst0' to read that tape you made?