I was at a conference recently where one of the speakers was talking about their services uptime during the past year. 99.998% uptime flashed on the screen to the applause of the mostly technical multitude! Some quick math told me that this system had experience only 10.512 minutes of unscheduled downtime during the previous 525,600 minutes (remember the song from “Rent”)! Very impressive numbers! However, it got me thinking about overall computer system reliability, how we put our faith in numbers and sort of arbitrarily create standards which are difficult and expensive to maintain.
Years ago, when competition was coming to our country’s landline telephone network , the “Bell” companies and AT&T touted that no other company or system could get close to their “Five 9s” in reliability. Again, doing the math, that’s only 5.256 minutes of unscheduled network downtime annually. “Ma Bell” was right. The landline networks (both voice and data) are “only” 99.995% reliable (averaging several government and industry surveys). So the average landline voice or data network can expect to have 26.28 minutes of unscheduled downtime annually.
used with permission from HP Technology at Work