Tim Bunnell wrote at 17:03 -0500 on Dec 13, 2008:
 > Folks,
 > 
 > We're running Amanda (version 2.5.1p1) on a Debian Linux system with an 
 > 8-tape AIT-2 library. We have around 314GB spread over two file systems 
 > that we are attempting to backup in one run across as many tapes as 
 > necessary. We're using gzip compression and expect it will take 5-6 
 > tapes to complete (there's a fair amount of audio and image data that 
 > doesn't compress too well).
 > 
 > I think we have the config files set up correctly, but it seems like no 
 > matter what we do, the run stops (after about 16 hours) and reports that 
 > it's out of tape. I don't think it has ever succeeded in spanning more 
 > than 4 tapes before giving us the error. I see nothing in the .debug 
 > output for the changer that looks different for any tapes it changes.
 > 
 > I'm sort of at a loss for where to start looking for the problem, and 
 > what to look for. Any suggestions from the list?

Do you really know the tape capacity for your tapes?
Some AIT-2 flavors are 36 GB, some are 50 GB, it seems.
36*8 < 314

Have you run amtapetype to verify?
 (see http://wiki.zmanda.com/index.php/Tapetype_definitions)
Do you have hardware compression off?