As you already know, each region consists of one or more datacenters that are in close proximity and connected via a low-latency network. Now, an Azure geography is defined as an area of the world that consists of one or more Azure regions. Some examples are United States, India, Asia Pacific, United Kingdom, etc. If we take the United States geography, it consists of several regions such as East US, West US, Central US, etc. So, an Azure geography ensures the data residency and compliance requirements are met. If you are an organization working with a US government organization, then you cannot store data outside of the United States. Similarly, the European Union has the General Data Protection Regulation (GDPR) where organizations cannot store personal data of the EU citizens outside EU member states. As an administrator, if your organization is GDPR compliant, you can pick a geography that is within the EU and stay compliant.

Azure pairs one region with another region within the same geography. Regional pairs play a vital role in business continuity and disaster recovery (BCDR). Whenever there is a planned update on the Azure platform, Azure rolls out the update sequentially across regional pairs. This guarantees that only one region in the regional pair is updated at a time and the other one can be leveraged for the recovery of the services if something goes wrong.

Figure 2.2 shows a graphical representation of regional pairs in Azure.

FIGURE 2.2 Graphical representation of Azure regional pairs

The following are some of the focus points about Azure regional pairs:

Physical Separation  Three hundred miles is the preferred distance between datacenters that are part of the regional pair; however, this might not be feasible in certain geographies. This isolation will diminish the probability of both regions being affected at the same time due to outages caused by natural disasters, power outages, etc.

Replication  Services like storage accounts provide georedundant storage (GRS). Using GRS, your data will be replicated to the paired region and thus provide reliability.

Recovery Order  If a mass outage happens, Microsoft will prioritize the recovery of one region out of every regional pair.

Serialized Updates  Azure planned updates are rolled out sequentially to the regions in a region pair. As the update is not done simultaneously, even if something goes wrong, one of the regions in the region pair can be used for recovery.

Data Residency  As the regions in a regional pair are part of the same geography, customers can get the benefit of regional pairs without breaking any of the data residency policies.

  • All region pairs have regions from the same geography; the only exception is Brazil South, and the paired region for Brazil South is South Central US. South Central US is part of the United States geography. However, the South Central US paired region is not Brazil South.
  • All region pairs are paired in both directions. One exception here is West India. West India’s pair is South India; however, South India’s secondary region is Central India.

Understanding regional pairs and incorporating them into your infrastructure will help you architect highly available solutions with business continuity in Azure. The complete list of Azure region pairs and how services can leverage regional pairs is available here:

https://docs.microsoft.com/en-us/azure/best-practices-availability-paired-regions

With that, we will move on to Azure accounts and subscriptions.