Describe Azure physical infrastructure
Azure's core architectural components can be broken down into two main groupings: the physical infrastructure and the management infrastructure. This unit covers the physical side — how Azure organizes its datacenters, regions, and availability zones to deliver reliable services worldwide.
Physical infrastructure
The physical infrastructure for Azure starts with datacenters. These datacenters are facilities with servers arranged in racks, with dedicated power, cooling, and networking infrastructure — similar to an on-premises datacenter, but at a much larger scale.
As a global cloud provider, Azure has datacenters around the world. However, you don't interact with individual datacenters directly. Instead, datacenters are grouped into Azure Regions and Azure Availability Zones that provide resiliency and reliability for your workloads.
The Global infrastructure site gives you a chance to interactively explore the underlying Azure infrastructure.
Regions
A region is a geographical area on the planet that contains at least one, but potentially multiple datacenters that are nearby and networked together with a low-latency network. Azure intelligently assigns and controls the resources within each region to ensure workloads are appropriately balanced.
When you deploy a resource in Azure, you'll often need to choose the region where you want your resource deployed.
Note
Some services or virtual machine (VM) features are only available in certain regions, such as specific VM sizes or storage types. There are also some global Azure services that don't require you to select a particular region, such as Microsoft Entra ID, Azure Traffic Manager, and Azure DNS.
Availability Zones
Availability zones are physically separate datacenters within an Azure region. Each availability zone is made up of one or more datacenters equipped with independent power, cooling, and networking. An availability zone is set up to be an isolation boundary. If one zone goes down, the other continues working. Availability zones are connected through high-speed, private fiber-optic networks.
Important
To ensure resiliency, a minimum of three separate availability zones are present in all availability zone-enabled regions. However, not all Azure Regions currently support availability zones.
Use availability zones for your workloads
When you run your own on-premises infrastructure, setting up redundancy means buying and maintaining duplicate hardware. With Azure, you can protect your workloads by spreading them across availability zones within a region.
You place your VMs, storage, databases, and other resources in one availability zone and replicate them to other zones within the same region. Keep in mind that there could be a cost to duplicating your services and transferring data between zones.
Azure services that support availability zones fall into three categories:
- Zonal services: You pin the resource to a specific zone (for example, VMs, managed disks, IP addresses).
- Zone-redundant services: The platform replicates automatically across zones (for example, zone-redundant storage, SQL Database).
- Non-regional services: Services are always available from Azure geographies and are resilient to zone-wide outages as well as region-wide outages.
Even with the additional resiliency that availability zones provide, it’s possible that an event could be so large that it impacts multiple availability zones in a single region. To provide even further resilience, Azure has Region Pairs.
Region pairs
Most Azure regions are paired with another region within the same geography (such as US, Europe, or Asia) at least 300 miles away. This approach allows for the replication of resources across a geography that helps reduce the likelihood of interruptions because of events such as natural disasters, civil unrest, power outages, or physical network outages that affect an entire region. For example, if a region in a pair was affected by a natural disaster, services would automatically fail over to the other region in its region pair.
Important
Not all Azure services automatically replicate data or automatically fall back from a failed region to cross-replicate to another enabled region. In these scenarios, recovery and replication must be configured by the customer.
Examples of region pairs in Azure are West US paired with East US and Southeast Asia paired with East Asia. Because the pair of regions is directly connected and far enough apart to be isolated from regional disasters, you can use them to provide reliable services and data redundancy.
Additional advantages of region pairs:
- If an extensive Azure outage occurs, one region out of every pair is prioritized to make sure at least one is restored as quickly as possible for applications hosted in that region pair.
- Planned Azure updates are rolled out to paired regions one region at a time to minimize downtime and risk of application outage.
- Data continues to reside within the same geography as its pair (except for Brazil South) for data-residency and compliance purposes.
Important
Most regions are paired in two directions, meaning they are the backup for the region that provides a backup for them (West US and East US back each other up). However, some regions, such as Brazil South, are paired in only one direction. In a one-direction pairing, the Primary region does not provide backup for its secondary region. Brazil South is unique because it's paired with a region outside of its geography. Brazil South's secondary region is South Central US. The secondary region of South Central US isn't Brazil South. Additionally, some regions (such as Italy North, Poland Central, and Israel Central) don't have a traditional region pair and instead rely on availability zones and geo-redundant storage for resiliency.
Sovereign Regions
In addition to regular regions, Azure also has sovereign regions. Sovereign regions are instances of Azure that are isolated from the main instance of Azure. You may need to use a sovereign region for compliance or legal purposes.
Azure sovereign regions include:
- US DoD Central, US Gov Virginia, US Gov Arizona, and more: These regions are physical and logical network-isolated instances of Azure for U.S. government agencies and partners. These datacenters are operated by screened U.S. personnel and include additional compliance certifications.
- China East, China North, and more: These regions are available through a unique partnership between Microsoft and 21Vianet, whereby Microsoft doesn't directly maintain the datacenters.