That'd just be one automatic system attempting to compensate for another going offline. Same question poses : what guarantees are in place to force maintenance

That'd just be one automatic system attempting to compensate for another going offline. Same question poses : what guarantees are in place to force maintenance of the second system (the one that never runs, except in exercises or disaster) ? How long until management demands the datacenters work with cooling that just provides, say, five nines of cooling capacity ? Can you guarantee that doesn't happen ? Do engineers at Google even care that that doesn't happen ? In other words, how long until Google loses the ability to pull the plug on this system from a physical perspective ? How long until Google loses that ability from an economic perspective (that turning it off would incur unacceptable costs) ?