I don't really have time to answer questions, but I did look at your build and from a cost perspective I believe in general 8TB drives are more cost effective than 4TB drives, and maybe it's just me, but water cooling in a machine that appears to be mission critical scares me. While most are quite reliable it only takes a drop of water from a faulty hose to take down your motherboard and potentially damage other components. You'd be without that system until replacement parts can be brought in an re-assembled. Finally, don't forget a UPS for power outages. Corrupt data in nobody's friend.