Arne Kaiser wrote:
[ ... ]
> I can write on the tape drive with tar, but if I try to restore from the
> tape only two or three files are restored.
> 
> Does anybody knows what I can do?

Aside from using "mt" as another response suggested, you might try adjusting 
the blocksize you use, perhaps to 32K or 63K via "tar -b 64" or "-b 126".  This 
larger blocksize helps keep the tape drive streaming.

(And yes, 63K is less intuitive than 64K, but it works faster for some tape 
drives, especially if compression is enabled.)

-- 
-Chuck