Steven Backus wrote at 10:20 -0600 on Aug  7, 2008:
 >   I've determined my drive can label tapes but can't read old
 > tapes.  I get the Input/Output error whenever trying to read a
 > previously labeled tape or dd out anything.  However, if I re-label
 > the tape it works again.  Does this indicate a failing drive?  Any
 > other ideas?

I've seen problematic behavior 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).

We set the block size for the tape unit to have variable length blocks
when doing amanda writes & reads.

In FreeBSD, that's 'mt blocksize 0' and for linux, 'mt setblk 0'.
(also we set hardware compression off)

I don't know if that will help in your case or not.

I assume you've done the simple test:

dd if=/dev/random bs=32k of=/tmp/foo count=1
mt -f /dev/<yourtape> rew
dd if=/tmp/foo bs=32k of=/dev/<yourtape> count=1
mt -f /dev/<yourtape> rew
dd of=/tmp/foo2 bs=32k if=/dev/<yourtape> count=1

diff /tmp/foo /tmp/foo2