Disk partition sizes on big disks.

[Spencer W. Thomas]

You didn't mention which Unix version you are running.  I know that on
4.1Bsd the restor program spent upwards of 50% of its time just clearing
out (and copying?) buffers.  Write, or steal, a buffer clear/copy
routine in assembler, and you'll probably see much better improvement. 
Our full saves are up to 26 tapes now!  (We've got a 6250bpi tape drive
on order, and will soon switch to 4.2, which should help too.)

=Spencer