Description of problem:

Tar hangs in D state on tape write, using Adaptec AHA-3960D SCSI card and Dell
PowerVault 122T.  I can't kill the process and can't 'ls /proc/[it's pid]/fd/'

Version-Release number of selected component (if applicable):

I'm using an FC3 system with kernel 2.6.11-1.14_FC3smp.

How reproducible:

Tar accepts a "-b" flag for the size of blocks to use in writing and reading. 
If I don't first set the tape drive to use a corresponding block size, tar hangs
immediate on invocations for read or write.  When I do set the corresponding
block sizes, the behavior becomes infrequent, but happens after about a day of
solid usage.

Steps to Reproduce:
1. tar cf /dev/tape files
2.
3.
  
Actual results:

Tar hangs.

Expected results:

Shouldn't hang.

Additional info: