Microsoft recommends usage of ARM for all new deployments in Azure. All new developments/features/services will be available in ARM going forward. But there are lot of services that are yet to be migrated to ARM. What if one of the services that you want to use is not currently available in ARM and you have already set up rest of your environment in ARM? In such a scenario, you can always set up a site to site VPN between the classic V1 VNET and the ARM VNET. This process is also well documented:
That being the case, what if we want to test the interoperability of services and you want to move few already set up VMS in ARM to classic? I know that it is not a very common scenario. Also it is not a recommended approach for production deployment, ARM is definitely the way to go. However, for enabling that test run you might very badly want to do before taking the plunge, we will look at the process of creating a new VM in classic portal from a hard disk of VM in ARM portal using Azure PowerShell.
First you will have to login to your Azure account
Enter the Source blob uri, ie location of the ARM VM's VHD
$sourceBlobUri = https://<Source-storagename> .blob.core.windows.net/vhds/<vhdname>.vhd
Set the Source context
$sourceContext = New-AzureStorageContext –StorageAccountName <Source-Storagename> StorageAccountKey <Storage access key>
In the destination context, give the name of your classic storage and its key
$destinationContext = New-AzureStorageContext –StorageAccountName <dest-storagename> -StorageAccountKey <Storage access key>
Copy the vhd to the destination storage
Start-AzureStorageBlobCopy -srcUri $sourceBlobUri -SrcContext $sourceContext -DestContainer "vhds" -DestBlob "rds1201647182929.vhd" -DestContext $destinationContext
This command will copy the VHD from the source storage to the container named 'vhds' in the destination storage. Ensure that your VM is in a stopped deallocated status during this procedure. Also if you want to The copy over took only a few minutes in my experience
Now we need to add this VHD as an OS disk in the gallery. Start with importing the publish settings file of the subscription
Download the publish settings file and import it
Import-AzurePublishSettingsFile '<Publish settings file name>'
Set the current subscription
Set-AzureSubscription -SubscriptionName "<Subscription name>"
Now add the OS disk
Add-AzureDisk -DiskName "OSDisk" -MediaLocation "https://<Source-Storagename> .blob.core.windows.net/vhds/<vhdname>.vhd" -Label "My OS Disk" -OS "Windows"
Refresh Azure classic portal
OS disk will be listed in the gallery. Now you can go ahead and create new VM from the disk!!
Note: The reverse of what is explained here is also possible, that is Migration from classic to ARM. There are well documented tools available for the same: https://github.com/fullscale180/asm2arm