I'm preparing to work with huge materials (AppleProRes422 HD), and i don't know does it possible editing with E-Sata external RAID 5 (8TB)?
MacPro Quad-Core Xeon
2GB 800 DDR2 FB-DIMM
AJA KONA 3 Box
A 8TB RAID5 should be an excellent choice for editing ProRes. Plenty of bandwidth.
You should be able to fit 50 hours of ProRes (for argument, let's say 1080p 23.98 Pro Res 422 HQ) on your drive, and still have plenty of room for formatting, RAID5, and leaving 20% overhead for performance.