Faster & Bigger Azure Backup for Azure VMs

Azure Backup recently rolled out an update to their service for protecting Azure VMs to improve backup speed, restore performance, and to add support for larger disks.

Support for Large Disks

Azure Backup didn’t support disks that were larger than 1 TiB (1 TB is the marketing measure of 1000 GB, and 1 TiB is the computer science measure of 1024 GiB). Those large disks must be popular – I know that people couldn’t get their head around the idea of a volume being spread across disk aggregation (they never heard of RAID, I guess) and wouldn’t touch Azure VMs because of this.

Today, Azure Backup, once upgraded by you, does support the large disks that Azure can offer (over 1 TiB).

Snapshot-Based Backup

People who deploy large VMs have seen that the traditional process of protecting their machines has been slow. Historically Azure Backup would:

  1. Create a snapshot of the virtual machine.
  2. Transfer the backup data from the storage cluster to the recovery services vault (standard tier block blob storage) over a network.

The snapshot was then dispensed with.

The backup was slow (the process of calculating changes, the network transfer and the write to standard storage), and restores were just as slow. It’s one thing for a backup to be slow, but when a restore is a 12 hour job, you’ve got a problem!

Azure made some changes, and now the process of a backup is:

  1. Create a snapshot of the virtual machine and keep 7 snapshots (7 backups).
  2. Use the previous snapshot to speed up the process of identifying changes.
  3. Transfer the backup data from the storage cluster to the recovery services vault (standard tier block blob storage) over a network.

Two things to note:

  • The differencing calculation is faster, speeding up the end-to-end process.
  • But after you upgrade Azure Backup, you can do a restore once the snapshot is complete, and while the backup job (transfer) is still happening!


7 snapshots are kept, and you can restore a virtual machine from either:

  • A snapshot from the last 7 backups)
  • A recovery point in the recovery services vault from up to the last 99 years, 9999 recovery points, depending on your backup policy.


Restoring from a snapshot should be much quicker, and this will benefit large workloads, such as database servers, where a restore is usually from as recent a backup as possible.

Distributed Disks Restore

The last new feature is that when you restore a virtual machine with un-managed disks (storage account disks) then you can opt to distribute the disks to different storage accounts.

Accessing the Features

A one-time one-way upgrade must be done in each subscription to access the new Azure Backup for IaaS VM features. When you open a (single) recovery services vault, a banner will appear at the top. Click the banner, and then read the blade that opens. When you understand the process, click Upgrade. A quick task will complete and approximately two hours later, your entire subscription will be upgraded and able to take advantage of the features described above.

Was This Post Useful?

If you found this information useful, then imagine what 2 days of training might mean to you. I’m delivering a 2-day course in Amsterdam on April 19-20, teaching newbies and experienced Azure admins about Azure Infrastructure. There’ll be lots of in-depth information, covering the foundations, best practices, troubleshooting, and advanced configurations. You can learn more here.

4 thoughts on “Faster & Bigger Azure Backup for Azure VMs”

  1. Great article Aidan. How to put this into a manageable system for say 1000 Windows clients? Do I need a 3rd party solution?

    1. For on prem? I’d advise you look at a third party solution that leverages Azure storage. That’s not Azure Backup then, so the Azure Backup pricing is irrelevant.

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