In post I’m going to take a look at creating and restoring Azure Virtual Machine snapshots for managed disks. These instructions are for Azure Resource Manager (ARM) virtual machines, for Azure Service Manager (ASM) virtual machines read this post. If you are looking for instructions to create and restore snapshots for unmanaged disks read this post.
Why use snapshots?
Snapshots can be used to duplicate a VM relatively quickly since it is faster than copying a blob. You still have to shutdown the source VM to ensure consistency but creating the snapshot only takes a few seconds. Once you have the snapshot you can use it to create new VMs or copies of the VHD blob while the source VM can be powered on again.
Snapshots can also be used as a backup strategy for VMs although Azure Backups provides better functionality with a lot less effort albeit a bit more expensive since you pay for the recovery vault.
The one advantage of snapshots is the ability to overwrite the OS disk without recreating the VM but only for unmanaged disks at the time of writing.
Managed Disk Snapshots
You can create snapshots in the Azure portal by selecting your managed disk from the disks main menu or the disks section on the VM blade.
Take note of the export button, you can use it to export the managed disk to a VHD blob which can be used to create unmanaged disks.
To create a snapshot using PowerShell call the New-AzureRmSnapshot command along with New-AzureRmSnapshotConfig to configure the snapshot options.
$mandisk = Get-AzureRmDisk -ResourceGroupName $rsgName -DiskName $diskname $snapshot = New-AzureRmSnapshotConfig -SourceUri $mandisk.Id ` -CreateOption Copy -Location $azureregion New-AzureRmSnapshot -Snapshot $snapshot -SnapshotName $Name ` -ResourceGroupName $rsgName
Restoring Managed Disk Snapshots
At the time of writing you couldn’t overwrite or change the managed OS disk on an existing VM but you can create a new managed disk from a snapshot and then create a new VM from the managed disk.
Update: You can now swap a Managed Disk on a VM by replacing the disk Id with another one. This still involves creating another disk from your snapshot and swapping it but at least you don’t have to recreate the VM anymore. Thanks to Ralph Herold for pointing it out to me.
$vm = Get-AzureRmVM -ResourceGroupName osrg -Name vm2 $disk = Get-AzureRmDisk -ResourceGroupName osrg -Name osbackup Set-AzureRmVMOSDisk -VM $vm -ManagedDiskId $disk.Id -Name $disk.Name Update-AzureRmVM -ResourceGroupName osrg -VM $vm
I assume you can do the same for data disks using Set-AzureRmVMDataDisk but I didn’t try it yet. Full documentation here.
You can create a new Managed Disk from a snapshot in the Azure Portal or PowerShell. In the Azure Portal select Create New Resource from the main portal menu and search for Managed Disks to create a new Managed Disk. There will be a Source Type dropdown where you can select Snapshot and you will see a list of your snapshots to use as the source for the new Managed Disk.
When the create disk operation is completed select the newly created managed disk and create a new VM from the disk.
If you want to script it in PowerShell the steps are basically:
- Retrieve the snapshot.
- Create a new disk configuration specifying the snapshot as the source.
- Create a new managed disk from the disk configuration and attach it to a new virtual machine.
If this is a data disk you can attach it to an existing VM instead of creating a new VM but OS disks can only be attached to new VMs.
... $snapshot = Get-AzureRmSnapshot -ResourceGroupName $rsg ` -SnapshotName $yoursnapshotname $diskconf = New-AzureRmDiskConfig -AccountType $storagetype ` -Location $snapshot.Location -SourceResourceId $snapshot.Id ` -CreateOption Copy $disk = New-AzureRmDisk -Disk $diskconf -ResourceGroupName $rsg ` -DiskName $osDiskName $vm = Get-AzureRmVM ... $vm = Set-AzureRmVMOSDisk -VM $vm -ManagedDiskId $disk.Id ` -CreateOption Attach -Windows ...
Full script can be found here.
Thanks for the powershell. Do you know if this can also be done via the Azure portal? They make it easy to create a snapshot but not seeing any obvious way to convert it to a managed disk from the portal.
Yes it can be done from the Azure Portal. Choose Create New Resource from the main portal menu and search for Managed Disks to create a new Managed Disk. There will be a Source Type dropdown where you can select Snapshot and you will see a list of your snapshots to use as the source for the new Managed Disk.
Quote “There will be a Source Type dropdown where you can select Snapshot and you will see a list of your snapshots to use as the source for the new Managed Disk”
Alright so, after this when you click [Create VM] are you saying you are creating a complete new VM ?? Don’t we have something like checkpoints (hyper-V) or snapshot restore (vmware), which can actually restore to the previous point rather than having an additional copy of VM?
With Managed Disk snapshots you can only create a new VM. To achieve checkpoints/snapshot restore functionality you’ll have to delete the existing VM and recreate it from the snapshot. If you use standard blob disks you can restore a snapshot and overwrite the existing blob while leaving the VM intact, more info here.
Hi, since a couple of weeks there is a Swap OS Disk function for managed disks. This together with the Swap Data Disk function should make it possible to have an easy way to restore a VM snapshot without all the hassle of re-creating the whole VM. @Francois, can you please update your script so we can have true VM snapshot functionality in Azure? Many thnx
Thanks for pointing it out, I updated the post.