Did The New York Stock Exchange Really Have to Shut Down For Super Storm Sandy?

Hurricane and Super Storms Sandy was rather historic in many regards. Certainly the size of the storm and the massive energy behind it along with the storm surges and deluge of rain was nearly of biblical proportions. But it was historic for another reason, it actually shut down the New York Stock Exchange for two days, something which hadn’t happened in 30 years. My question is why did they need to shut it down at all? Shouldn’t something as important as the NYSE have redundancies?