The datacenters are connected to the internet through Gigabit ethernet connections from separate backbone providers, who each run fiber optic cables into the data center through separate entry points.
To guard against line failure or intrusion, the data center is staffed 24 hours a day. Movement throughout the facility is escorted at ALL times. There is 24x7 closed circuit monitoring of all areas and entrances. Between the cameras, access control, and the security team, the datacenter facilities are pretty secure.
The total incoming power is a multiple of what is required to run the datacenter. There is an ATS (Automatic Transfer switch) in place to automatically kick in a generator in case of a power failure. The datacenters are also equipped with redundant UPS systems to ensure clean power.
Redundant A/C systems, each running at a fraction of their capacity, keep the server rooms cool. The units are alternated so that each one is kept in optimal condition.
The datacenters are equipped with specialized fire detection and protection systems meant specifically for protecting servers as using ordinary water based systems would cause just as much damage as fire.