Hello Kent,

  K> Here's what bonnie reports with 2940UW and three IBM DDRS-34560's

See...

       http://www.storage.ibm.com/hdd/support/ddrs/ddrs_ps.pdf

      ...which describes their sustained data rate as "8.3-13.3 MB/s".

  K> The Adaptek literature and the IBM drive literature claim
   > theoretical 40Mb/s.

That's for the SCSI bus though, not for the drive itself.  Bonnie's
reporting about 8.9Mb/s write and 11.1Mb/s read, which seems to fit
with their above claim quite well.

  K> I would expect that under optimal conditions, running a benchmark
   > such as bonnie, one should be able to do better than 12981K/sec
   > with a pair of striped drives though...

I have no significant experience with RAID and would not attempt to
predict the throughput of any given array.

Regards,
  - Andy Ball.