You'll probably need at least 4 capacitors the size of a Saturn 1B third stage, wired in parallel to do what you are describing . The cabling would need to be pretty hefty as well...

Capacitors (for some reason) seem to have become the be-all and end-all of supply problems in this board; don't forget, they only store charge. Without a resistance in series, a capacitor can deliver all it's charge in one burst (current is flow of charge). So adding capacitors to your PSU will make other problems, like the inrush current required to fill them when you turn it on, like the potential shock risk when the system is turned off, and they still won't give you much help with your problem.

By sticking your RAID array inside your CPU, you are at risk of causing the problem the array is designed (in one aspect anyway) to address - CPU power failure. If your main power supply goes out, your RAID array should not be affected and at least store any data saves committed before the failure. Stick 'em in the same box and you'll loose the lot if the single PSU goes down.

Cheapest, sanest solution - buy yourself another CPU casing with a high power PSU that has a peak rating above the maximum current draw of all the disks at active state. Sling a cable across from your CPU RAID controller, and Bob's yer proverbial.

Doesn't cost much, reduces the risk of SPOF failures, and makes my blood pressure go down a bit

One of the few remaining Mk1 owners... #00015