Ok, this is just plain nuts. 800 volts DC, at the megawatt power supply levels, implies fault impulses of more than a megajoule. Google tells me that's about 2

Ok, this is just plain nuts. 800 volts DC, at the megawatt power supply levels, implies fault impulses of more than a megajoule. Google tells me that's about 2 hand grenades worth of boom. That's an optimistic lower bound. The resulting copper plasma cloud is a burn and inhalation hazard, along with the overpressure. Let's say you get a 10 kiloamp fault current, this will then induce voltages everywhere you don't want it to go. If all the interconnects are fiber, that's really not a problem, but you have to have everything EMP shielded if you don't want boards popping randomly after such an event. The "efficiency" of removing the extra power conversions also removes filtering and surge suppression. It's entirely possible that one power supply over-voltage takes out half of your racks. The MOSFETs used tend to fail closed instead of open, making failures far worse than a simple outage. Very smart people are making very smart mistakes.