Migrating VMs from Hyper-V 2008 or 2008 R2 to Hyper-V 2012 R2

There has been a recent explosion of questions around this in the Hyper-V TechNet forum over the past two weeks.  So I decided that I would blog about this a bit.

The primary question is: How can I migrate from Hyper-V 2008 (or Hyper-V 2008 R2) to Hyper-V 2012 R2.

There are lots of very well meaning folks that provide the advice of: "Export your VMs from your 2008 era Hyper-V Server and then Import those VMs to your 2012 R2 Hyper-V Server."

Obviously, they never tested this.  Because, IT DOES NOT WORK.

First of all, lets test this common advice:  Export a VM from Hyper-V 2008 / 2008 R2 and import direct to Hyper-V 2012 R2.

1. Create your VM Export
2. copy the export folder to a Hyper-V 2012 R2 system
3. attempt to import.

You will instantly get this:  "Hyper-V did not find virtual machines to import from location"
And you look, and everything is right there in that folder.  What gives!

The next piece of well meaning advice is to create a new VM configuration using the existing VHD in that export folder. 
(this will work, but if you have snapshots you are screwed - all of that snapshot history is lost, and lots of folks connect to the incorrect virtual disk and freak out that years of history was lost.)
 
If you were going to do this in the first place, why not just copy out the VHDs and save yourself some effort and be done with it.  This is viable option 1.

Here is the option that many folks overlook / are not aware of (as it was a new feature of Hyper-V 2012 R2:

Copy the VM folder direct from the Hyper-V 2008 R2 system to the Hyper-V 2012 R2 system and Import. 

Hyper-V 2012 R2 reads the XML configuration and imports the VM asking you a couple questions to fix things up. 
This is viable option 2 (actually the easiest if you have additional hardware with Hyper-V 2012 R2 already built).

We could stop there but not to be left without choices;  you can in-place upgrade from your Hyper-V 2008 / 2008 R2 era system to Hyper-V 2012 and then again to Hyper-V 2012 R2.  This will update the VM configurations as you go, and you will be all good.  Now we have a viable option 3.

Suppose that all you have is a VM Export.  Then what? 
Remember that error message at the beginning; Hyper-V 2012 R2 cannot read the VM export from Hyper-V 2008 / 2008 R2.  Now, we have other options.

Take your VM folder that you exported from your Hyper-V 2008 R2 system and copy it to a Hyper-V 2012 system.  Then import.  Success!

Now what?  You want Hyper-V 2012 R2.  You have a few viable options to take this from Hyper-V 2012 to Hyper-V 2012 R2: 

In-place upgrade the Hyper-V 2012 system to Hyper-V 2012 R2.  This is viable option 4.
Export the VMs, then import them to your Hyper-V 2012 R2 system.  This is viable option 5.

Thinking out of the box, are there other options?

I am always assuming that you have backups of your systems.  And you have tested restoring those backups, and you know those backups are indeed good and useful.  This gives another option. 
Restore your VMs to the Hyper-V 2012 R2 system as new VMs.  This becomes viable option 6.

There you have it.  Six options to test and choose from.  All of which are considered supported. And will save you the panic of realizing that going straight from a Hyper-V 2008 / R2 VM Export to 2012 R2 will not work.