Azure SLAs and Composite SLAs
Read Azure service SLAs, calculate composite SLA for a multi-service architecture, and understand how adding redundancy can increase or decrease the overall SLA.
What Is an SLA?
A Service Level Agreement (SLA) is a formal commitment from Microsoft defining the minimum uptime and connectivity guarantee for each Azure service. SLAs are expressed as a percentage — for example, 99.9% means the service will be available at least 99.9% of the time in a given month. If Microsoft fails to meet the SLA, customers are eligible for service credits as compensation.
Reading Azure SLA Documents
Each Azure service has its own SLA document published at azure.microsoft.com/en-us/support/legal/sla/. When reading an SLA, pay attention to: the uptime percentage, the conditions required to achieve it (e.g., deploying across two or more instances), and the credit table that specifies how much credit you receive for each level of underperformance.
# Common Azure SLA percentages:
# Azure Virtual Machines (single instance, Premium SSD): 99.9%
# Azure Virtual Machines (two instances, different AZs): 99.99%
# Azure SQL Database (Business Critical): 99.99%
# Azure Blob Storage (RA-GRS): 99.99%
# Azure App Service: 99.95%