Very slow tape drive

[Hywel Mallett]

I have a Tandberg SLR60 tape drive, connected to an Adaptec 29160
controller. The drive can backup using dump at around 3MB/s, which is
acceptable, if a bit slower than I was expecting.
I have a problem though in that I have a large number tapes I need to
read the data from. The tapes were written using cpio (on SCO
OpenServer), and when trying to read from the tapes using cpio, I only
obtain transfer rates of 150KB/s maximum.
iostat shows that during both the cpio and the dump, sa0 is managing
around ~290 transfers per second, but during the dump each transfer is
10KB, but during the cpio, each dump is 0.5KB.
My basic question is do these figures sound normal? Is there a limit of
300 tps on a scsi bus?
If so, how could I make the cpio faster? My thoughts included restoring
from tape to a file, then using cpio on the file.
TIA,
Hywel