Special:Badtitle/NS100:Why can I write new labels to my tapes but can't read the old ones?

Check your blocksize. This behavior can occur when the tape unit is set to have a particular block size (that may not match at read time what was used to write a tape). For example, in your rc.conf file you may have "/bin/mt -f /dev/nst0 defblksize 0" and you should verify this command is working correctly. As another example, some users put "options st buffer_kbs=256" in /etc/modprobe.conf to force a 256K fixed blocksize rather than deal with variable size.