Virtual machines are protected in virtual protection groups (VPGs). A VPG is a group of virtual machines that you group together for recovery purposes. For example, the virtual machines that comprise an application like Microsoft Exchange, where one virtual machine is used for the software, one for the database, and a third for the Web Server require that all three virtual machines be replicated to maintain data integrity.

Any virtual machine whose operating system is supported in both the protected site and recovery site can be protected in a VPG.

Once a virtual machine is protected, all changes made on the machine are replicated in the remote site. The replicated virtual machines in the remote site can be recovered to any point in time defined for the VPG or if a period further in the past is required, an offsite backup can be restored.

When a VPG is created, a replica of each virtual machine disk in the VPG is created under a VRA on the recovery site. These replica virtual disks must be populated with the data in the protected virtual machines, which is done by synchronizing the protected virtual machines with the recovery site replicas. The time taken for synchronization between the protected and recovery sites will depend on the size of the virtual machines.

After the initial synchronization completes, only the writes to disk from the virtual machines in the protected site are sent to Azure. These writes are stored by the Virtual Replication Appliance (VRA) in the journals in a storage account for a specified period, after which they are promoted to the replica virtual disks managed by the VRA, which are also in storage account.

The number of VPGs that can be defined on a site is limited only by the number of virtual machines that can be protected. Each site can manage a maximum of 300 virtual machines.