High Availability 9’s

This is very important to understand what is high availability 9’s, This is a measurement of high availability  where you can tell how much downtime is feasible for your organization for a Year(annually).

the calculation is as follows

=Total Hours in a Year-(Total Hours in a Year* # of 9’s)/100

where Total Hours in a Year =365(days)*24 Hours =8760 Hours

so in this way if you have 2 -9’s ie. 99% the down time duration could be.

=8760-(8760*99)/100

=87.6 hours

=3 Days and 15 Hours

simillarly if you have 3 – 9’s means 99.9%

=8760-(8760*99.9)/100

=8.76 hours (8 hours and 45minutes)

and so on.

Number of 9’s Availability Percentage Hours Total Annual Downtime
2 99% 87.6000 3 days, 15 hours
3 99.9% 8.7600 8 hours, 45 minutes
4 99.99% 0.8760 52 minutes, 34 seconds
5 99.999% 0.0876 5 minutes, 15 seconds
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