Restore an Azure Virtual Machine’s Hard Disks

In this post, I’ll show you how to restore just the disks of an Azure virtual machine. This is useful if you want to restore a virtual machine to an availability set, or restore it as a different series/size.

Restoring to Availability Sets

For some reason that I do not know, we cannot restore a virtual machine to an availability set in Azure. It probably has something to do with the restriction in ARM that prevents a VM from being able to join an availability set after creation (vote for change here).

As a workaround, Azure Backup allows you to restore the disks, and then use those disks to create a new virtual machine (metadata) that is joined to the availability set. On the official docs pages, there is some pretty messy looking PowerShell to re-create the VM from those disks.

Thanks to some features of Managed Disks, if you have used managed disks for the VM, then you don’t need to go anywhere near that nasty PowerShell or JSON! I’ll post about that soon.

Restoring Disks

Browse to to the recovery services vault, open it, go to Backup Items > Azure Virtual Machine, and select the VM in question. Below is a screenshot of my web server in Azure. Click Restore VM.

A blade with recovery points appears. Choose a restore point, i.e. a point in time from when you want to restore from, and click OK.

The Restore Configuration blade appears. Choose Restore Disks as the Restore Type, and choose a storage account as the Staging Location. Click OK to start the backup job.

Some time later, the disk(s) of the virtual machine are restored as blobs in a container in the storage account. You’ll also find a JSON file with details of the disk(s) that were restored.

By the way, if you cannot tell which of the VHD blobs is your OS disk, download the JSON file and open it in Notepad (VS Code refuses to open it for me). The “osDisk” setting will tell you the path of the VHD blob that was the original data disk.

Microsoft’s solution would have you restore the virtual machine using PowerShell and that JSON file. I’ve read through it – it’s not pretty! My solution, in a later post, would create managed disks from the VHD blob(s), and then create a VM from the OS disk … and that’s nice and easy using the Azure Portal and a few mouse clicks.