18.4 Prerequisites for Using Azure Availability Sets

An Azure Availability Set is an Azure service that provides high availability to two or more member VMs by deploying them in different fault domains and update domains. Fault domains ensure that the VMs run on different host servers, compute racks, storage units, and network switches. Update domains ensure that maintenance outages for host hardware do not occur at the same time.

NOTE:VMs must be created in the Availability Set. You cannot add an existing VM to an Availability Set.

Using Azure Availability Sets is optional. No availability set is configured by default.

PlateSpin Migrate supports using pre-defined Azure Availability Sets for target VMs. You cannot create Availability Sets in Migrate.

Before you configure workloads for the target VMs that you want to add to an Availability Set:

  • Use the Azure portal to create and define the Availability Set in a resource group for the specified target location.

  • You can use an Availability Set in combination with Azure Managed Disks only if you enable the Use Managed Disks option in the Availability Set definition.

When the first VM is created in the Availability Set, Azure selects the physical hardware that will be used in the target Azure location. Thereafter, Azure limits the cloud instance sizes and networks that can be used for future member VMs accordingly.

NOTE:If you have multiple VMs configured for the same empty Availability Set, the first cutover VM determines the Azure limits based on the configuration characteristics of that VM. PlateSpin Migrate might prompt you to choose different cloud instance sizes or networks after the Azure limitations are enacted.