Five 9s is telcom and data center lingo meaning 99.999% availability. It’s equivalent to 5 minutes of downtime per year. The PSTN (public switched telephone network) is designed to five 9s going back to the days of fanatical engineers at Ma Bell. Remember when we all had AT&T and Bell Telephone? The phone simply always worked.

Last week Amazon was down for a while. According to the info in this PC World article, it seems they average a couple of hours per year of downtime. That’s approximately 99.98% availability. Not five 9s. In fact less than four 9s.

This raises an important question: what would we do if there was an AWS outage on any critical service we might have there? Who would I call? Would I be able to get timely and accurate status updates to inform my boss or ministries that rely upon it? The whole thing gives me pause.