writing to 3ware escalade uses up 100% cpu time in system.

Hello,

I'm using a 3ware 8506-4LP controller with 4 250GB harddrives in
Raid 0.  All space is in a single slice, separated into 1GB swap and
the rest into twed0s1d which is mounted under /space...

When I do 
    ``dd if=/dev/zero of=/space/test bs=1000000 count=10000''
the twed0 maxes out at 70MB/sec and (according to systat) 70% usage.
Unfortunately my system goes to 100% cpu usage at the same time.

My kernel is running with all Whitnesses and Invariants switched
off.  I had them on before, but then I got only 30% usage and
30MB/sec when cpu weht to 100%.

I would really love to be able to use the aproximate 100MB/sec at
100% usage of the twed0, without using all that much cpu.


-- Robert S.