20 years ago I read a postmortem of Tandem and their Non-Stop Unix. A core take-away for me was: "Computer hardware has gotten way more reliable than it was."

20 years ago I read a postmortem of Tandem and their Non-Stop Unix. A core take-away for me was: "Computer hardware has gotten way more reliable than it was." combined with "The leading cause of outages has become operators making mistakes."