So they have 2 different sources of power coming in. And generators. They do mention the UPS is only for "certain functions", so I guess it's not enough to handle full load while generators spin up if the 2 primaries go out. Or perhaps some failure in the source switching equipment (typically called a "static transfer switch").
Some detail on different approaches: https://www.donwil.com/wp-content/uploads/white-papers/Using...
If they claim tier4, then they basically have everything in n+n configuration.
I used to work next door to a "major" cable TV station's broadcast location. They had multiple generators on-site, and one of them was running 24/7 (they rotated which one was hot). A major power outage hit, and there was a thunderous roar as all of the generators fired up. The channel never went off the air.
Our main computer lab had a serial UPS that was online 100% of the time, though the inverters where under a very light load. If the mains even acted 'weird' (dips, bad power factor, spikes) the UPS jumped full on, and didn't revert to main power until the main was stable for some duration of time. The UPS was able to carry the full lab (which was quite large) for about two hours, allowing plenty of time for the generator to fire up.
The UPS ran a lot, and because the main was 'weird', the outages were often short, the generator wouldn't even start during the first ten minutes of UPS coverage. Of course, the rest of the building would be dark, other then emergency lighting.
I was a embedded firmware engineer, and our development lab was directly on the wall behind the UPS. When it fired into 100% mode, it roared, mostly from cooling. It was sort of a heads up that the power was likely to fail soon.
A few minutes seems correct for one place I worked.
This was back in the 90's, before UPS technology got really interesting. Our system was two large rooms with racks and racks and racks of car batteries wired together. When the power went out, the batteries took over until the diesel generator could come online.
I saw it work during several hurricanes and other flood events.
I always found the idea of running an entire building off of car batteries amusing. The engineers didn't share my mirth.
I wonder if a lot of AWS dc design in this area predates the battery grid storage revolution with (what my impression is) a far faster adaptation/switchover time than a generator spin up, and possibly software systems that work to detect and switch over quickly?
AWS can claim it will be best of breed, but they aren't going to throw out a DC power redundancy investment (or threaten downtime) that they can't wring more ROI on.
Tesla apparently did some early pilot stuff: https://www.datacenterdynamics.com/en/analysis/teslas-powerp...
Maybe it could affect people buying services as well.
