Azure Availability Zones are a key component of the platform’s high availability and fault tolerance strategy. They allow you to deploy applications and data across physically separate data centers within a single Azure region, ensuring resilience and continuity in case of infrastructure failures.
What Are Availability Zones?
An Availability Zone is a physically separate zone within an Azure region. Each zone is made up of one or more independent data centers, each with its own power, cooling, and networking infrastructure.
- A minimum of three Availability Zones exists in supported Azure regions.
- These zones are geographically close but located several miles apart to prevent a single point of failure from affecting all zones.
- Low-latency, high-speed private network connections link these zones, enabling fast and reliable communication.
Availability Zones are critical for building highly available applications. If one zone goes down due to a hardware failure or natural disaster, the others remain operational, keeping your services online.
Zonal Redundant Storage (ZRS)
To enhance redundancy, Azure supports Zonal Redundant Storage (ZRS), which stores multiple copies of your data across different Availability Zones.
- ZRS protects your data from zone-level failures.
- Depending on the service, ZRS may be included in the pricing or require additional cost.
ZRS is especially useful for mission-critical workloads that require both high availability and durability.
Availability vs. Availability Sets
It’s important to distinguish between Availability Zones and Availability Sets:
- Availability Zones span multiple data centers across a region.
- Availability Sets are limited to a single data center and protect against failures within that center (e.g., rack or hardware failures).
Because of their broader fault domain separation, Availability Zones offer stronger protection than Availability Sets. For more on redundancy options, refer to #topic 30#.
Limitations and Considerations
- Not every Azure region supports Availability Zones.
- Redundancy using zones must be intentionally configured; it is not always automatic.
- You should verify if your region supports zones when planning high availability deployments.
To learn more about how Availability Zones contribute to Azure’s architecture, see AZ-900: Describe Azure regions and AZ-900: Describe the benefits of high availability and scalability in the cloud.
Conclusion
Availability Zones provide a robust way to ensure uptime and resilience by isolating workloads across separate physical locations. By leveraging ZRS and other built-in Azure features, organizations can significantly reduce the risk of service disruption.
Interested in building resilient solutions with Azure? Learn how in our AZ-900 video course – or go back to the topics in the AZ-900 exam.
Please click here to find out more about Microsoft’s AZ-900 exam.
