CERC 1.5/6ch and high load averages, poor performance

[Neil Jones]

I have a (new) PowerEdge 1800 with a CERC 1.5/6ch controller.  It has
a single 4 volume RAID 5 array, which is also controlled through Linux
LVM; the system runs Red Hat Enterprise 4.

I've noticed that when any application begins to do a lot of disk I/O
(e.g., MySQL), the load on the machine jumps up to a very high number
(currently, 13).  The applications themselves use very little memory
and there is no swapping going on --- all disk I/O is coming from
explicit file I/O from an application. The only processes that seem
active are the I/O-heavy application, kjournald, and (oddly) kswapd.

Has anybody seen this problem before, and if so, what did you do about it?
-- 
..Neil