Platform i386

I've defined 3 disks in a raid-5 with the following raid config file :

START array
1 3 0
START disks
/dev/wd1b
/dev/wd2b
/dev/wd3b
START layout
# sectPerSU SUsPerParityUnit SUsPerReconUnit RAID_level
32 1 1 5
START queue
fifo 100

which works fine.  I also did the raidctl(s) to initialize the
raidframe driver and initialize the parity info (takes about
an hour).  However, that all worked.  Then I made a file system
on the resulting raid device (newfs -b 8192 -f 1024 -c 32 /dev/rraid0b).
That also takes about 15 to 20 minutes.  Then I mounted it, and
everything seems to work. Great!  Then I try a simple command:
dd if=/dev/zero of=/space/test1 bs=256k count=1024
The raid device started recording data and then just stopped.  Any
attempt to look at that file system or raid device just hangs.

Am I doing something obviously wrong?

TIA,
Paul Newhouse