>> Neither really. AFAIK tar has never worked for multi-volumes.
>
>Wrong.
>I used tar with multi volume option for half an year to transport files
>from the Sun workstations at our university to my Amiga home.

Well, then your tar must have been a Gnutar in disguise :)
Tar does not support multi-volumes at all. I have done quite
a lot research on that after I bought a Tape-drive. Well, 
actually before I bought the drive. I was raving mad since
gnutar on the Amiga did not support multi-volume creation
(Which it does under Unix), so I bought the tapedrive.

>From the MAN file of tar:
DESCRIPTION
     tar saves and restores multiple files on a single file (usually a
                                                ^^^^^^^^^^^
  

Cheers,
Karl Ivar Dahl    (____)       
                  ( O O)   No one was sure whether	     
       /-----------\  /   M.C. Escher's cow had four      
      / ||       |  \/          legs or eight               
     /  ||       ||||             
    *   ||||-----||||  *from 'COWS' by fazam@skat.usc.edu
        ^^^^     ^^^^