After banging my head against this a while longer, I thought I'd change tack and see where it led.
In BIOS I deleted my RAID5 volume and created a RAID1 volume with 2 of the 3 disks. After booting into Win7 I created a NTFS partition on the RAID1 volume. During reboot, for some reason BIOS thought that the new volume was RAID5 with a dead disk. So I recreated the RAID1 volume and the NTFS partition, but this time unchecked the "quick format" option. Reboots henceforth saw the RAID1 volume.
Now when I booted ubuntu, the raid volume showed up in /dev/mapper without me having to do anything. Disk Utility showed the devices as "RAID Component". This is progress.
Disk Utility also showed the component devices under"Peripheral Devices". In addition, they showed up individually under "Places" in the menu bar. Not good.
Mounting the raid volume resolved that. First, I determined the UUID of the volume by running blkid and looking for the /dev/mapper entry. In /etc/fstab I added:
# RAID 1 volume
UUID=16D4FA0ED4F9F03B /shared ntfs auto,rw,noexec,dev,suid,posix=1 0 3
Ran:
sudo mount -a
It barked:
fuse: failed to access mountpoint /shared: No such file or directory
Solved this by:
sudo mkdir /shared
Then the mount finished without error.
Now Disk Utility shows just the raid volume under "Peripheral Devices".
Given the number of postings about troubles with RAID0, coupled with my own experience with RAID5, I'm thinking that striping is at the root of the problems. RAID1 is mirroring and no striping, and it works fine with no extra effort. Striping crosses devices, and I suspect that there is a compatibility problem between how BIOS/Intel Matrix Manager layout the devices and what dmraid expects.
While not what I had wanted originally, I'll live with the RAID1 instead of RAID5.
I've also posted on the Ubuntu forums. Hopefully the ICH10R RAID issues will get addressed in due time.
David