Disaster Recovery: Staying Afloat in the Face Of Unspeakable Tragedy: A year after 9/11, business continuity is more than a full-time job for CIOs.(Citigroup's Bill Krivoshik)

No matter how thorough a disaster recovery plan, there's always something that's overlooked or underestimated, particularly when the calamity pushes beyond anyone's reasonable worst-case scenario. But what unfolded on the morning of September 11, 2001, was incomprehensible.

"The plan always was that something may happen where we'd lose a building, or a floor. But on September 11, we were out the six or seven buildings that we had downtown," says Bill Krivoshik, CTO, global investment management for the unit of Citigroup that handles asset management and private banking.

Krivoshik's unit, which has nearly 1,200 employees, was located in 7 World Trade Center, which collapsed several hours after the Twin Towers, which were across the street. Despite the destruction of its offices and the temporary dislocation of as many as 16,000 Citi employees in lower Manhattan, the unit and the entire institution were back in …