Chain Of Failure

Independent events

Underneath every system outage is a chain of events like this. One small issue leads to another, which leads to another. Looking at the entire chain of failure after the fact, the failure seems inevitable. If you tried to estimate the probability of that exact chain of events occurring, it would look incredibly improbable. But it looks improbable only if you consider the probability of each event independently. A coin has no memory, so each toss has the same probability, independent of previous tosses.