Upgrading your Virtual Machine version

When you upgrade to Windows 10 – there is a second manual step that is needed to upgrade your virtual machine version.  You need to shutdown the virtual machine and then either select to “Upgrade Configuration Version” through the UI – or run the Update-VMVersion PowerShell command.
In the past we would automatically upgrade the virtual machine configuration as part of upgrading Hyper-V – so why have we made it a manual step in this release?
Well, many people need to work with virtual machines that move between different versions of Hyper-V.  This has not been possible in the past.  Now, if you need to move a virtual machine back and forward between Windows 10, Windows 8.1 and Windows Server 2012 R2 you can.  If you choose not to upgrade the virtual machine configuration – we will ensure that everything about the virtual machine remains backwards compatible.  Even saved states and checkpoints.
So why should you upgrade your virtual machine version?  To access new features of course!  Virtual machines created on Windows 8.1 / Windows Server 2012 R2 use version 5.0 configurations.  Virtual machines created on Windows 10 use version 6.2 configurations.  Here is a little table of features in Windows 10, and the minimum virtual machine configuration version that they need:

Feature NameMinimum VM version 

Hot Add/Remove Memory

Hot Add/Remove Network Adapters

Secure Boot for Linux VMs

PowerShell Direct

Production Checkpoints

You can read more about this here: https://msdn.microsoft.com/en-us/virtualization/hyperv_on_windows/user_guide/migrating_vms