SLA for Azure Virtual Machines

• 99.99% : for all Virtual Machines that have two or more instances deployed across two or more Availability Zones in the same Azure region
• 99.95% : for all Virtual Machines that have two or more instances deployed in the same Availability Set
• 99.5% : for any Single Instance Virtual Machine using Standard SSD Managed Disks for Operating System Disk and Data Disks
• Details : https://azure.microsoft.com/en-us/support/legal/sla/virtual-machines/

Availability diagram of Azure Virtual Machine

Note: Microsoft does not reveal actual location of datacenters, I assumed just for sake of explanation!

Availability options

• Availability Zones
• Availability Sets
• Virtual Machine Scale Sets

Availability Zone

• “Availability Zone” is a fault-isolated area within an Azure region, providing redundant power, cooling, and networking
• Each region has two or more Availability Zones and each zone has a set of Datacenters
• Fault-tolerant to protect from datacenter failure

Availability Zone for VM

• While creating VM in Azure portal, there is “Availability option” and you can select “Availability Zone” as Availability option
• To get SLA 99.99%, you must select 2 or more zones
• Maximum 3 zones can be selected

Availability Zone as ‘Availability Option’ while creating Azure Virtual Machine

Availability Sets

See: Azure Virtual Machine Availability Sets

Scale Sets

See: Azure Virtual Machine Scale Sets

Auto scaling with high SLA

• Both “Auto-scaling” & SLA 99.99% can be achieved with combination of “Virtual Machine Scale Sets” and “Availability Zone” (2 or more zones)
• Create load balancer and Virtual Machine Scale Set, and then provision each VM with 2 or more zones