What is the reliability of the five nines, four nines, and three nines that are often mentioned in operation and maintenance?
Three 9s: (1-99.9%) * 365 * 24=8.76 hours, which means that the maximum possible service interruption time of the system in one year of continuous operation is 8.76 hours. Four 9s: (1-99.99%) * 365 * 24=0.876 hours=52.6 minutes, which means that the maximum possible service interruption time of the system in one year of continuous operation is 52.6 minutes. Five 9s: (1-99.999%) * 365 * 24 * 60=5.26 minutes, which means that the maximum possible service interruption time of the system in one year of continuous operation is 5.26 minutes.
One 9: (1-90%) * 365=36.5 days, which means that the maximum possible service interruption time of the system in one year of continuous operation is 36.5 days. Two 9s: (1-99%) * 365=3.65 days, which means that the maximum possible service interruption time of the system in one year of continuous operation is 3.65 days. Six 9s: (1-99.9999%) * 365 * 24 * 60 * 60=31 seconds, which means that the maximum possible service interruption time of the system in one year of continuous operation is 31 seconds.