The right answer is turn them all off - anything important is in a redundant data center. But odds are they don't have that.
If a redundant data center isn't an option, then you should put more into ensuring the system is resilient - fireproof room (if a server catches on fire it can't spread to the next - there are a lot of considerations here that I don't know about that you need to figure out), plenty of backup power, redundant HVAC, redundant connections to the internet - and you should brainstorm other things that I didn't think of.
If a redundant data center isn't an option, then you should put more into ensuring the system is resilient - fireproof room (if a server catches on fire it can't spread to the next - there are a lot of considerations here that I don't know about that you need to figure out), plenty of backup power, redundant HVAC, redundant connections to the internet - and you should brainstorm other things that I didn't think of.