Re: failure to think it through
Heh. We had *just* finished migrating all our servers from one data center to a new one, when we had a power outage at the new site. The big 3 phase UPS worked fine, the generator kicked in, but we couldn't get into the data center. Why? because the door controllers that operated the keycards and locks were off-line, and the locks were all 'fail secure'. To add injury to insult, the cubicles that were put into the building just outside the data center were also not on generator power, so we were kinda screwed until we could get to a different site and remote into the servers to make sure they were OK.
That got fixed rather quickly.