Understanding SLA (Service Level Agreement) is very important after you choose to start from scratch OR migrate your application to Cloud.

You can find the SLA provided by Microsoft for its Azure services here.

Usually the SLAs will be 99.9 (three9s) to 99.999 (five 9s). At a first glance, you can think there is not a major difference in them. However when you are hosting a production application, it is very important to understand what the 9’s really mean w.r.t the downtime.

Here is a table for you to understand SLA vs Downtime

SLA percentage	Downtime per week	Downtime per month	Downtime per year
99	1.68 hours	7.2 hours	3.65 days
99.9	10.1 minutes	43.2 minutes	8.76 hours
99.95	5 minutes	21.6 minutes	4.38 hours
99.99	1.01 minutes	4.32 minutes	52.56 minutes
99.999	6 seconds	25.9 seconds	5.26 minutes