about power/network redundancy, people dont understand or know how things really work. MA probably dont either. its fine all the time they are up, but these systems are rarely tested - how can they with out taking systems offline or warning that there maybe an outage?
i have gone through two power loss situations with top UK data centre, on both occasions a thirdparty screwed somthing up and the redundant power didnt failover or failed over but some circuits didnt (ie fused). Ive also had engineer in the floor cavity screw up and take out the power to the routers and on another occasion the office redundant power simply didnt cut in because it did get the signal to do so and had never been tested. couple of weeks ago a contractor tore through a major network link in East London, knocking out literally tens of thousands of lines, many companies found redundant lines where on the physical underground route. it happens, networks are not perfect and do not route around problems in the way the theory says they will (because carriers dont necessarily reroute traffic).
the important thing is that the power stays up long enough for systems to shut down gracfully, so there is no loss of data. uptime is secondry concern. you will not find a datacentre supplier in the world that promises 100% uptime, and you shouldnt believe anyone who does.