Azure Availability Zones and Regions

Azure is backed up by large datacenters interconnected into a single large network. The datacenters are grouped together, based on their physical proximity, into Azure regions. For example, datacenters in Western Europe are available to Azure users in the West Europe region. Users cannot choose their preferred datacenter. They can select their Azure region and Azure will allocate an appropriate datacenter.

Choosing an appropriate region is an important architectural decision as it affects:

Let's discuss each of these points in detail.

Availability of resources

Not all resources are available in every Azure region. If your application architecture demands a resource that is not available in a region, choosing that region will not help. Instead, a region should be chosen based on the availability of the resources required by the application. It might be that the resource is not available while developing the application architecture, and it could be on Azure's roadmap to make it available subsequently.

For example, Log Analytics is not available in all regions. If your data sources are in Region A and the Log Analytics workspace is in Region B, you need to pay for the bandwidth, which is the data egress charges from Region A to B. Similarly, some services can work with resources that are located in the same region. For instance, if you would like to encrypt the disks of your virtual machine that is deployed in Region A, you need to have Azure Key Vault deployed in Region A to store the encryption keys. Before deploying any services, you need to check whether your dependency services are available in that region. A good source to check the availability of Azure products across regions is this product page: https://azure.microsoft.com/global-infrastructure/services.

Data and privacy compliance

Each country has its own rules for data and privacy compliance. Some countries are very specific about storing their citizens' data in their own territories. Hence, such legal requirements should be taken into consideration for every application's architecture.

Application performance

The performance of an application is dependent on the network route taken by requests and responses to get to their destinations and back again. The location that is geographically closer to you may not always be the region with the lowest latency. We calculate distance in kilometers or miles, but latency is based on the route the packet takes. For example, an application deployed in Western Europe for Southeast Asian users will not perform as well as an application deployed to the East Asia region for users in that region. So, it's very important that you architect your solutions in the closest region to provide the lowest latency and thus the best performance.

Cost of running applications

The cost of Azure services differs from region to region. A region with an overall lower cost should be chosen. There is a complete chapter on cost management in this book (Chapter 6, Cost management for Azure solutions), and it should be referred to for more details on cost.

So far, we have discussed how to choose the right region to architect our solution. Now that we have a suitable region in mind for our solution, let's discuss how to design our virtual networks in Azure.