Seems like more testing is in order:<p>> <i>Upon the outage, both banks immediately activated IT disaster recovery and business continuity plans.</i><p>> <i>"However," according to Tan, "both banks encountered technical issues which prevented them from fully recovering their affected systems at their respective backup datacenters – DBS due to a network misconfiguration and Citibank due to connectivity issues."</i><p>Perhaps regularly flipping between them on a regular basis, at least for a short time, so the 'passive' part of the active-passive pair gets some work, is worth considering.