How to Calculate SLA for a Product

When we work against multiple Azure Services for a Single Product we need to handle the SLA (Service Level Agreement) carefully. It is not min or max or the average of SLA per services. Let's take an example,

Table 1

Service	SLA
App Service	99.95%
Azure Active Directory	99.9%

 

What these % means,

%	Downtime/week	Downtime/month	Downtime/year
90%	16.8 hours	72 hours	36.5 days
99%	1.68 hours	7.2 hours	3.65 days
99.9%	10.1 minutes	43.2 minutes	8.76 hours
99.99%	1.01 minutes	4.32 minutes	52.56 minutes
99.999%	6.05 seconds	25.9 seconds	5.26 minutes
99.9999%	0.605 seconds	2.59 seconds	31.5 seconds

 

All the SLA of Azure is defines at https://azure.microsoft.com/en-us/support/legal/sla/

Based on Table 1 if an application uses both the Azure Services then the composite SLA of the Application would be

0.9995 x 0.999 = 0.9985005

Hence 99.85%. So it is neither 99.95% nor 99.9% it is altogether different.

Also one need to consider if there is anything in Application which defines its SLA.

Namoskar!!!