A common question for newcomers to Microsoft’s Azure platform is what’s the difference between an availability zone and an availability set?
An availability zone is a unique physical location within one Azure region, and provides high-availability for your application and infrastructure. Each zone is independent and has physically isolated power, cooling, and networking from other zones within the same region.
Different Azure services have varying levels of support for availability zones. Some will automatically replicate between zones, while others will require you to choose the zone to connect to.
Availability zones aren’t available within all Azure regions – in fact, currently there are only 10 regions across the United States, Asia and Europe that support availability zones:
- Central US
- East US
- East US 2
- West US 2
- North Europe
- UK South
- West Europe
- France Central
- Japan East
- Southeast Asia
On the other hand, an availability set is a concept that only applies to virtual machines. A set allows you to isolate virtual machine (VM) resources from one another when deployed, meaning your VMs will run across multiple machines and racks. This will help to avoid a hardware failure bringing down your entire application, and also means that outages from Microsoft updates won’t cause your application issues.
Unlike an availability zone which applies at the data centre level, an availability set only applies within the same data centre.