To Err is Human

We argue for the importance of human error as a significant and oft-overlooked factor in system dependability, and contend that human behavior must be considered in both dependability benchmarks and high-dependability system designs. We support our claims with data illustrating that human-induced failures consistently account for half of all outages, and show that human error accompanies even the simplest system operation and maintenance tasks. We then consider how human behavior might be accounted for in both dependability benchmarks and in the designs of dependable computer systems.