Its super interesting to dive into the world of cryptocurrency mining, where some DCs are getting PUE of 1.1 or better with a buildout that's basically amounts to shelves and box fans.
No generators, just eat the downtime. No batteries. No 24/7 staff. No racks, just shelves (folded sheet metal is cheap). Security varies from farm to farm.
These servers don't need to run cool, as long as you are in a climate that doesn't get over 100 degrees you can get away with fans and no AC.
Per-site reliability (beyond a stated/assumed 95%, which is right around the "I put a computer on my desk" level) isn't a design goal, though. You can argue with their math or their assumptions, but you can't say they're wrong for not designing in the reliability features you list above.
I think it very much depends on the desk. I mean, power alone at my home just barely reaches three nines. Internet connectivity glitches out occasionally. I'll fat finger configurations and reinstall stuff for some more hours a year. It all adds up.
You're right that you can take the same hardware, add a $70 UPS and some thought and care, and do much, much better. But my point was only that "95%" is a trivially achievable goal even in the most naive setups, which makes me treat their analysis with a little more credence than most folks here.
No generators, just eat the downtime. No batteries. No 24/7 staff. No racks, just shelves (folded sheet metal is cheap). Security varies from farm to farm.
These servers don't need to run cool, as long as you are in a climate that doesn't get over 100 degrees you can get away with fans and no AC.