Hi Yuk Leong Chow,
Configure Backup for Azure Virtual Machine Scale Sets: Ensure you have a Recovery Services Vault in the same region as your VMSS. When you back up data in Azure, you store that data in an Azure resource called a Recovery Services vault. The Recovery Services vault resource is available from the Settings menu of most Azure services. The benefit of having the Recovery Services vault integrated into the Settings menu of most Azure services is the ease of backing up data.
For detailed information with steps, please check: Back up multiple virtual machines by using the Azure portal,
Back up Azure VMs in a Recovery Services vault
Check that your VMSS is set to Flexible Orchestration Mode before proceeding. You need appropriate permissions as the Backup Contributor role. First create a Recovery Services Vault and then Define a Backup Policy to enable Backup for Each VMSS Instance.
Restore and Create New Virtual Machine Scale Sets from Backup: Azure Backup does not directly restore an entire VMSS, but it allows you to restore VM instances, and then you can create a new VMSS using those resources.
Go to Recovery Services Vault, Go to Backup items > Azure Virtual Machine. Select the backed-up VMSS instance then Click on Restore VM. For new VM, Azure creates a standalone VM using the backup and for disks, you'll get managed disks in your subscription which you can use to create a custom image.
For detailed information with steps, please check: restore VM
How to restore Azure VM data in Azure portal, Restore a VM with Azure CLI
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