well depends, i prefer raid 2 so its an exactly copy of my other hard drive, so if it fries i can just change it over and it runs perfectly like nothing ever happened. Though because of how raid 5 it evenly distributes it across all 5 disks, so your right it would not save your operating system.

That would def work 2, i wish i could pay for a ssd, they have become ridiculously expensive nowadays though.