WHS does not officially support a RAID setup, so not even sure if this would work.
But out of curiosity did you try installing WHS and adding the RAID drivers for your motherboard during the install? (not sure if you get prompted during a WHS install for extra drivers, but if there is a prompt then at that point you could try and
add the raid drivers for your motherboard see if that changes anything)
You're not really supposed to need RAID for a WHS install, most people use a smaller disk for the system drive, which WHS partitions into C and D. (C for the system, and remaining space on D for the storage pool). Then you would add your two
2tb drives as part of the storage pool. Once your shares are created on the storage pool drives you would then turn on Folder Duplication for redundancy. The only thing not protected using this method is the system drive. If the system drive
were to fail then you are supposed to perform a system reinstallation which is supposed to preserver the data on your storage pool drives, and just re-install the OS.
