Modeling the Effect of Reliability on Performance: A Performability Tutorial

In a two-processor computer system, a single processor failure may not cause the system to crash. But, if the second processor is used continuously, rather than as a standby, this processor failure can still cause a substantial performance degradation. While some systems are always either fully operational or "out-of-service", many high reliability systems, like the two-processor system, degrade gracefully. In such systems, sub-system or component failures that do not cause a total system failure, might still reduce the system's capacity or performance.