Four Instances, Two Data Centers, One Bug: When Redundancy Isn't Independence
The Pennsylvania NG911 incident highlights the risks of common-mode failures. Redundancy's independence must be evaluated.
Pennsylvania's NG911 disruption illustrates how four instances were affected by a single OS defect. Redundancy is effective against independent failures, but a common-mode failure can lead to total system failure. Engineers must assess whether their systems are truly independent.