Azure Paired Regions
Intro
Have you ever wondered how Azure protects your data and applications from disasters? Azure has a smart strategy that involves using different groups of datacentres within and across regions. These groups are called availability zones and regional pairs, and they help Azure achieve high availability and disaster recovery.
Availability Zones
Availability zones are separate datacentres within the same region that have their own power, cooling, and networking systems. They are close enough to have fast connections but far enough to avoid being affected by the same local issues. For example, if one zone has a power outage or a fire, the other zones can still keep your services running.
Regional Pairs
Regional pairs are two regions that are paired together for cross-region replication. This means that Azure can copy your data and applications from one region to another automatically or manually, depending on the service. This way, if a whole region goes down or becomes unreachable, you can still access your data and applications from the other region.
Azure has many regions around the world, and each region belongs to a geography. A geography is a boundary that defines where your data resides and how it is protected by law and tax regulations. Azure tries to pair regions within the same geography, except for a few exceptions. For example, Brazil South is paired with South Central US, which is in a different geography.
Azure also makes sure that the paired regions are physically isolated from each other, meaning they are at least 300 miles (483 kilometers) apart. This reduces the chance that a natural disaster, civil unrest, or a network outage can affect both regions at the same time.
If you want to know the Regional Pair for your chosen Azure Region, then you can refer to this Microsoft article. For example I deploy a lot of Azure resources into UK South, and by default when I choose to create something like a storage account with GRS replication, it replicates it to UK West:
Conclusion: Which Option Should I Choose?
Azure gives you the option to use availability zones and regional pairs for your services, but it doesn’t force you to do so. You can choose to use only one region or multiple regions that are not paired. You can also create your own disaster recovery solution by using Azure services such as AzCopy, Azure DNS, and Azure Traffic Manager. However, I strongly recommend that you use availability zones and regional pairs whenever possible, as they offer the best protection and availability for your data and applications.
And to be honest, it is a fine balancing act, and you need to understand what your business & requirements are before you can make a decision. Some workloads you may choose to keep within a single Availability Zone in a single region, whereas for some critical workloads, you may want to be available across regions. Designing and architecting the right solution for the workload is key here, and it is worth spending more time to understand the requirements before making such decisions. You also need to review what availability options there are, and the cost implications. Do the research upfront, and you will be glad that you did!