Have you tried running a SMART testing utility against the failed drive? Smartmontools comes on most Linux installation disks and there should also be plenty WinRE-based bootable systems with similar tools. If none work, in your BIOS, is there an option to turn Intel RST off? For instance, to switch it from RAID mode to AHCI mode which should disable RST's OROM. I would likely try booting from each of the drives that make up the mirror array and see if it does anything if the first option fails. In the least, using smartmontools to run a long disk-check may see if the drive has actually failed or not. In the least, I would poll the SMART log but running a long test on it would be more useful. Knoppix is still very-much useful at this point for a LiveCD for diagnostics.