I work for a large OEM company, we option a bunch of our servers with SATA RAID Controllers which have support for linux. A device driver for the SATA RAID card fixes this problem. However some manufacturers of the cards don't have linux support, therefore no drivers.
Intel don't have linux drivers for their RAID cards, and according to them aren't planning on releasing any yet, or the source code.
Adaptec however do have linux support, and they are the cards which once you install the driver (linux dd) see's only the mirrored pack and installs no probs.
We've spoken to Intel a number of times asking for ETA's on driver with no luck.
I reckon you give Silicon Image a call asking them if they are going to release drivers.
Also you've probably already found, if you do go ahead and install linux onto one of the drives in the mirrored pack (when you see two at the installation stage), after the reboot it doesn't boot up, we found this was because it didn't know where to write the boot loader.
Let me know if you get any further with this, we push the Adaptec cards for this reason, if the customer wants to run linux.