Availability % and downtime mapping
When people talking about system availability, it reflects to an agreed downtime. The mapping is as following: Availability % Downtime per year 99% 3.65 days 99.5% 1.83 days 99.9% 8.77 hours 99.95% 4.38 hours 99.99% 52.60 minutes 99.995% 26.30 minutes 99.999% 5.26 minutes (Table source: https://docs.microsoft.com/en-us/learn/modules/deploy-sql-server-virtual-machine/2-explain-iaas-options-deploying-azure)
For solution involves mulitple system with different availabilities, the maximum availability of the overall solution is the smallest availability. However, you can utilise Availability Zones to increase overall availability.
Posted by John Liu Sunday, November 7, 2021