tape driver, shell script

els

i write a srcipt to copy disk data to tape driver, just like this:
......
tar cvc /dev/st0/xxx.tar.gz /backup
......
but, my tape driver, sometimes it is '/dev/st0', sometimes it is '/dev/nst0',
so i must update the script usually!
who can tell me how to resolve the problem?
and, '/dev/st0' has what different as '/dev/nst0'?

thanks!