Bug 67157

Arjan, Stephen, Doug:  Any suggestions?

For the most part, this is limited by tape read speeds.  I've seen two things in
the past result in *very* slow tape read speeds.  1) Bad tapes that are marginal
and result in lots of error recovery actions in order to actually read the data.
 You can usually tell if this is the case because the tape drive will stop
streaming, rewind a bit, then start again and it will do this little backup and
retry thing a *lot*.  It kills performance and there isn't anything linux can do
about it.  2) Writing a tape in a block mode that the tape drive can't read back
very well.  For example, setting the block size on st0 to 0 then writing to tape
and then restoring from that tape may work significantly slower than setting the
block size on st0 to 32k and then writing out the backup and then restoring.  In
this case, the only thing to do is to do a little experimentation with various
tape drive settings like block size and compression and perform a backup with
each setting and then see how speedily the restore can be done with each
setting.  Once you find a setting that performs well, stick with it as your default.

If neither of these solves your problem, then reopen the bug report.  However,
until there is something else to go on, this doesn't sound like a bug to me, it
sounds like hardware issues.