Due to some of the recent restrictions within Azure on deployments, some of you may have had to deploy VM sizes that were not idea, or didn’t exactly fit your needs. As part of that, you may have had to limit your choice in Managed Disk SKU too.

For example, I had to deploy a D8v3 for a customer and use Standard SSD until restrictions were lifted. I have no change the VM SKU to D8Sv3 and the disks to Premium SSD. For some people this is just about performance, but don’t forget, the financial SLA for VMs requires they run Premium SSD Managed Disks. Another solid reason to use them!

So, if you find yourself in a situation where you need to change the SKU, how can you do it? There are two ways I recommend, both require the VM to be deallocated so you may have to plan an outage, however the process is quick, so just a short one should be required.

Method 1: Via the Portal

This works best for individual, or a small number of VMs.

So, first up, if your VM needs to be resized to support Premium SSD, you should do that. Via the Portal, you simply stop the VM, choose your new size, and apply. One tip however, on the overview page of the VM blade, ensure you hit refresh so that the updated size is shown. For some reason, the Disk blade needs that to show that correctly or you cannot update your Disk SKU.

Next, choose the Disk blade, and select the disk you want to change. Click the Configuration option and simply choose the correct SKU from the drop down menu. This works for moving between any SKU by the way, as long as the VM size supports. Make sure to click Save.

Now, back to your VM blade, click Start and you’re done! VM and Disk updated.

Method 1: Via the Shell

This works best if you need to make multiple changes at once, save some time. As always with my shell examples, I am using Powershell, but the same actions can be carried out with CLI.

The below shows how to switch all Disks for a VM between tiers. In this example, we’re changing them to Premium, you can change that with the $storageType variable. Note, the below will Stop the VM for you and start it again. The VM must be running a Size that supports Premium in advance.

# Name of the resource group that contains the VM
$rgName = 'yourResourceGroup'

# Name of the your virtual machine
$vmName = 'yourVM'

# Choose between Standard_LRS and Premium_LRS based on your scenario
$storageType = 'Premium_LRS'

# Stop and deallocate the VM before changing the size
Stop-AzVM -ResourceGroupName $rgName -Name $vmName -Force

# Get all disks in the resource group of the VM
$vmDisks = Get-AzDisk -ResourceGroupName $rgName 

# For disks that belong to the selected VM, convert to Premium storage
foreach ($disk in $vmDisks)
{
	if ($disk.ManagedBy -eq $vm.Id)
	{
		$disk.Sku = [Microsoft.Azure.Management.Compute.Models.DiskSku]::new($storageType)
		$disk | Update-AzDisk
	}
}

Start-AzVM -ResourceGroupName $rgName -Name $vmName

And that’s it, you’re done!

The above example code was taken and edited slightly from the Docs article on this. The article includes multiple options for changing between tiers, single disks vs multiple etc. Check it out here – https://docs.microsoft.com/en-us/azure/virtual-machines/windows/convert-disk-storage