Regions and Availability Zones in Azure

• 02/23/2021
• 8 minutes to read
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Microsoft Azure services are available globally to drive your cloud operations at an optimal level. You can choose the best region for your needs based on technical and regulatory considerations: service capabilities, data residency, compliance requirements, and latency.

Terminology

To better understand regions and Availability Zones in Azure, it helps to understand key terms or concepts.

Regions

A region is a set of datacenters deployed within a latency-defined perimeter and connected through a dedicated regional low-latency network. Azure gives you the flexibility to deploy applications where you need to, including across multiple regions to deliver cross-region resiliency. For more information, see Overview of the resiliency pillar.

Availability Zones

An Availability Zone is a high-availability offering that protects your applications and data from datacenter failures. Availability Zones are unique physical locations within an Azure region. Each zone is made up of one or more datacenters 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 from single-points-of-failure. With Availability Zones, Azure offers industry best 99.99% VM uptime SLA. The full Azure SLA explains the guaranteed availability of Azure as a whole.

An Availability Zone in an Azure region is a combination of a fault domain and an update domain. For example, if you create three or more VMs across three zones in an Azure region, your VMs are effectively distributed across three fault domains and three update domains. The Azure platform recognizes this distribution across update domains to make sure that VMs in different zones are not scheduled to be updated at the same time.

Build high-availability into your application architecture by co-locating your compute, storage, networking, and data resources within a zone and replicating in other zones. Azure services that support Availability Zones fall into two categories:

• Zonal services – where a resource is pinned to a specific zone (for example, virtual machines, managed disks, Standard IP addresses), or
• Zone-redundant services – when the Azure platform replicates automatically across zones (for example, zone-redundant storage, SQL Database).

To achieve comprehensive business continuity on Azure, build your application architecture using the combination of Availability Zones with Azure region pairs. You can synchronously replicate your applications and data using Availability Zones within an Azure region for high-availability and asynchronously replicate across Azure regions for disaster recovery protection.

Region and service categories

Azure's approach on availability of Azure services across regions is best described by expressing services made available in recommended regions and alternate regions.

• Recommended region - A region that provides the broadest range of service capabilities and is designed to support Availability Zones now, or in the future. These are designated in the Azure portal as Recommended.
• Alternate (other) region - A region that extends Azure's footprint within a data residency boundary where a recommended region also exists. Alternate regions help to optimize latency and provide a second region for disaster recovery needs. They are not designed to support Availability Zones (although Azure conducts regular assessment of these regions to determine if they should become recommended regions). These are designated in the Azure portal as Other.

Comparing region types

Azure services are grouped into three categories: foundational, mainstream, and specialized services. Azure's general policy on deploying services into any given region is primarily driven by region type, service categories, and customer demand:

• Foundational – Available in all recommended and alternate regions when the region is generally available, or within 90 days of a new foundational service becoming generally available.
• Mainstream – Available in all recommended regions within 90 days of the region general availability; demand-driven in alternate regions (many are already deployed into a large subset of alternate regions).
• Specialized – Targeted service offerings, often industry-focused or backed by customized/specialized hardware. Demand-driven availability across regions (many are already deployed into a large subset of recommended regions).

To see which services are deployed in a given region, as well as the future roadmap for preview or general availability of services in a region, see Products available by region.

If a service offering is not available in a specific region, you can share your interest by contacting your Microsoft sales representative.

Services by category with Availability Zones

As mentioned previously, Azure classifies services into three categories: foundational, mainstream, and specialized. Service categories are assigned at general availability. Often, services start their lifecycle as a specialized service and as demand and utilization increases may be promoted to mainstream or foundational. The following table lists the category for services as foundational, mainstream. You should note the following about the table:

• Some services are non-regional. For information and a list of non-regional services, see Products available by region.
• Older generation of services or virtual machines are not listed. For more information, see documentation at Previous generations of virtual machine sizes
• .Services are not assigned a category until General Availability (GA). For information, and a list of preview services, see Products available by region.

Specialized Services

As mentioned previously, Azure classifies services into three categories: foundational, mainstream, and specialized. Service categories are assigned at general availability. Often, services start their lifecycle as a specialized service and as demand and utilization increases may be promoted to mainstream or foundational. The following table lists specialized services.

Next steps

• Regions that support Availability Zones in Azure
• Quickstart templates