Running applications and systems that are available to users for consumption whenever they need is one of the topmost priorities for CIO's. They want their applications to be operational, functional, and continue to be available to their customers even when some untoward event happens, and this is the theme for this chapter—Designing High Availability. Keeping the lights on is the common metaphor used for High Availability. Achieving High Availability for applications is not an easy task and organizations have to spend considerable time, energy, resources, and money to achieve this. And even when using them, there are still chances and risks that their implementation does not produce the desired results. Azure provides a lot of High Availability features for virtual machines (VMs) and PaaS services. In this chapter, we will go through the architectural and design features provided by Azure for ensuring High Availability for applications and services.

In this chapter, we'll cover the following topics:

• Azure availability sets:
  • Fault domain
  • Upgrade domain
• Azure load balancer
• Azure application gateways