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.
# of 9′s | % | Hours of downtime |
2 | 99 | 87.6 |
3 | 99.9 | 8.76 |
4 | 99.99 | 0.876 |
5 | 99.999 | 0.0876 |