So Bob, what’s your redundancy plan if a motherboard or graphics card fails? Nothing is impervious to failure anywhere in the system. RAID 5 is a good compromise between a single drive failing and speed. There are other RAID configurations that will give slightly more security but may slow your drives as well.
As with anything, buy good quality, have redundancy strategies and if you have the budget for a spare MacPro in case one dies, then you might afford a second RAID5 setup that mirrors your main drive system and constantly backs up the work drive. i have three different RAID devices here and often back up current media and project files to a second RAID.