Water and servers don’t mix. Storms can do more than cut the power to a data center, they can also breech walls, flood, or otherwise damage a center. A natural disaster like Hurrican Sandy can also make it difficult for staff to even be there to do their jobs, and can delay the arrival of replacement parts, fuel for generators, and so on.

Two posts at Data Center Knowledge do a good job of outlining how they prepared, and what actually happened.