On March 13th, 2018 Microsoft introduced the ability to backup Virtual Machines with disks bigger than 1TB. Unfortunately, they did not enable this feature by default and you have to upgrade your VM backup stack. Luckily this is easy to do and does not impact your current backup jobs. You can upgrade via the Azure portal or via PowerShell.

With the upgrade you do get some extra features as well:

• Large disk support – Now you can backup VMs with disk sizes up to 4TB(4095GB), both managed and unmanaged.

• Instant recovery point – A recovery point is available as soon as the snapshot is done as part of the backup job. This eliminates the need to wait to trigger restore till data transfer phase of the backup is completed. This is particularly useful in scenarios where you want to apply a patch. Now you can go ahead with the patch once the snapshot phase is done and you can use the local snapshot to revert back if the patch goes bad. This is analogous to checkpoint solution offered by Hyper-V or VMware with the added advantage of having snapshot also securely stored in the backup vault.

• Backup and Restore performance improvements – As part of this new announcement, we are also retaining the snapshots taken as part of the backup job for seven days. This will help us to compute the changes between two backup jobs in an efficient manner to reduce the backup time. These snapshots can also be used to trigger restore. Since these snapshots are available locally, restore process will eliminate the need to transfer the data back from the vault to the storage account, thus reducing the restore time from hours to minutes. Ability to configure the retention snapshots stored locally will be available in upcoming releases.

• Distribute the disks of restored VM – If you are using unmanaged VM, you might have noticed that during restore, we restore all disks to the same storage account. We are adding a capability where you can tell us to distribute those disks to the same set of storage accounts as the original one of your VM to reduce the reconfiguration needed post-restore.

From: https://azure.microsoft.com/en-gb/blog/large-disk-support/

Upgrade via the Portal

Note: This is a one-directional per subscription process and can not be changed back.

In the Azure portal navigate to the Recovery Services Vault

Click one of your vaults

You should now see an orange banner at the top of the overview blade. Click it.

A new blade will appear, Click the big blue Upgrade button.

After up to two hours your VM backup stack will upgraded and you will be able to backup large VM disks.

Upgrade using PowerShell

Navigate to https:\\shell.azure.com to open up the Azure Cloud Shell.

Select your directory if you have multiple.

Once loaded make sure you are in the PowerShell shell and not the Bash shell. It should be blue.

Type the following PowerShell command to list your subscriptions.


Take a note of the subscription you want to upgrade and then use the following PowerShell to select the subscription. Change the -TenantId to match yours.

Select-AzureRmSubscription -TenantId 'd114100a-8f19-4861-bcf0-491f4dd2de19'

To register this subscription for the upgrade use the following PowerShell.

Register-AzureRmProviderFeature -FeatureName "InstantBackupandRecovery" -ProviderNamespace Microsoft.RecoveryServices

After up to two hours your VM backup stack will upgraded and you will be able to backup large VM disks.

There we have it two simple ways to unable large disk backup in Azure. I hope you found this article helpful. If you have any questions please reach out.

Pixel Robots.

I’m Richard Hooper aka Pixel Robots. I started this blog in 2016 for a couple reasons. The first reason was basically just a place for me to store my step by step guides, troubleshooting guides and just plain ideas about being a sysadmin. The second reason was to share what I have learned and found out with other people like me. Hopefully, you can find something useful on the site.

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