Example: Achieving Five Nines

OK, why is this so hard?

First, note that 80% of unscheduled outages are caused by people or process errors [SCOTT, many others] --> There is only a 20% window in which to optimize component reliability.
Why? Because in order to increase component reliability, we typically add complexity (remember the relationship between robustness and complexity). This effectively narrows the 20% window.

Bottom line: Optimization frequently increases complexity, which increases the likelihood of people and process failures