Azure Backup uses the Recovery Services vault to protect virtual machines by creating restore points stored in Azure. Before a virtual machine can be backed up, it must have the Azure Backup extension (also called VMBackup extension) properly installed and configured on the VM.
According to Microsoft Learn – “Back up and restore encrypted virtual machines” and “Back up Azure VMs with the Azure Backup service”, the backup process for a VM requires the following:
“When you enable backup for an Azure virtual machine, the Azure Backup service installs an extension on the VM to coordinate the snapshot and backup process. If the extension is missing or not installed properly, backups cannot be triggered for that VM.”
Explanation of the Scenario
You already have a Recovery Services vault protecting VM1 and VM2.
You now need to add VM3 and VM4 to the same vault for protection.
Before they can be added, you must ensure that:
The VMs are running in the same region as the Recovery Services vault (because a vault can only protect resources within its region).
The VMBackup extension is installed and registered on each VM.
If the backup extension is missing or not configured correctly, Azure Backup cannot communicate with the VM to take snapshots or register it in the vault.
Once the extension is properly configured, you can then enable backup from the Recovery Services vault without needing to create a new vault, policy, or storage account — because all those resources already exist and can be reused.
Other Options Explained
A. Create a new Recovery Services vault: ❌ Not necessary unless the new VMs are in a different region from the existing vault.
C. Create a storage account: ❌ Azure Backup automatically manages backup storage within the vault; no separate storage account is required.
D. Create a new backup policy: ❌ Not needed unless you want a different backup schedule or retention. You can use the existing policy.
✅ Final Verified Answer:
B. Configure the extensions for VM3 and VM4.
Microsoft Learn Extract (Supporting Documentation):
“To enable Azure Backup for virtual machines, the Azure Backup extension must be installed. This extension coordinates the snapshot and backup process and is installed automatically when backup is enabled.”
“If the extension is not installed, you must configure it before enabling protection.”
(Source: Microsoft Learn — Back up Azure VMs with the Azure Backup service, Azure Recovery Services vault overview)
