When either selecting a data center as a co-location facility or designing a new one from scratch, what would your ideal specification be?
Fundamentally, diversified power sources, multiple ISPs, redundant generators, UPS, cooling, and physical security are all desireable.
What are the additional key requirements that someone might not consider on the first pass?
What are the functional details someone might not consider during the initial high level design?
I'd like to approach this from the perspective of designing a large data center or seeking a facility that was designed perfectly from an infrastructure perspective. This question has already been addressed with smaller facilities and workspace considerations here.