I agree that an OS on the 10 isn't the best way to use it, and stuffing an SSD (if a fast OS/applications disk is desired and within budget), can be placed in the empty optical bay. No risk of the ICH throttling either. 🙂
You could get another pair of 2TB disks and JBOD them in an external enclosure (or stripe, though for backup, I prefer JBOD, as if you lose a disk, you don't lose all the data, just what was on the failed disk). And you should be able to restore that off of the primary data location (odds of a dual primary and backup failure are possible, but not all that likely - usually due to a power problem of some kind when it does). Cheap to do as well (inexpensive enclosure, perhaps Port Multiplier based, and an eSATA card).
Just a thought anyway... 😉