Review availability zones
Availability zones are a high-availability offering that protects your applications and data from datacenter failures. An availability zone in an Azure region is a combination of a fault domain and an update domain.
Consider a scenario where you create three or more virtual machines across three zones in an Azure region. Your virtual machines are effectively distributed across three fault domains and three update domains. The Azure platform recognizes this distribution across update domains to make sure that virtual machines in different zones aren't updated at the same time.
You can use availability zones to build high-availability into your application architecture by colocating your compute, storage, networking, and data resources within a zone and replicating in other zones.
Things to know about availability zones
Review the following characteristics of availability zones.
Availability zones are unique physical locations within an Azure region.
Each zone is made up of one or more datacenters that are equipped with independent power, cooling, and networking.
To ensure resiliency, there's a minimum of three separate zones in all enabled regions.
The physical separation of availability zones within a region protects applications and data from datacenter failures.
Zone-redundant services replicate your applications and data across availability zones to protect against single-points-of-failure.
Things to consider when using availability zones
Azure services that support availability zones are divided into two categories.
| Category | Description | Examples |
|---|---|---|
| Zonal services | Azure zonal services pin each resource to a specific zone. | - Azure Virtual Machines - Azure managed disks - Standard IP addresses |
| Zone-redundant services | For Azure services that are zone-redundant, the platform replicates automatically across all zones. | - Azure Storage that's zone-redundant - Azure SQL Database |
Tip
To achieve comprehensive business continuity on Azure, build your application architecture by using a combination of availability zones with Azure region pairs.