Vmware V center migration of VM to new ESXi Server causes windows reactivation

ESX doesn't mask all of the hardware details to the guests, so windows would see the change in the processor.  When you powered on the VM, did you get a question if you moved or copied the VM, too?  That would have changed the GUID depending upon how you answered it.

If you changed it to virtual hardware version 7, that would be another change that Windows would key off of.

Well when I did the migration from within V center it didnt ask if I copied or moved the VM. I know you get this option if you copy the files manually.

I would have thought that if you do a miogration from within V center - it wouldnt cause this issue ?  Or did this happen because I had two different ESXi hosts (Dell 2850 and dell 2950)

I assume I wont have issues if I just reactivate?>

anyone else any comments on reactivation when moving VM's

You are correct.  You will not have any issues after re-activating.

There are enough differences between the host Dell 2850 and Dell 2950 two cause a Re-activation, because the hardware has changed. If you were going to keep both in the "farm", it's likely you would have issues using vMotion between them without using CPU Masks.

one of the elements of Windows Activations is using the Processor Type and Serial Number, as this has now changed, this is likely to cause a re-activation.

Are you running a retail or OEM license on your Windows? If that is the case I am not surprised you are asked to reactivate. If it is an OEM license it shouldn't be on VMware to start with as that license is irrevokably tied to its original hardware. If it is a retail license you should be able to reactivate and run fine. However retail licenses still have some limits to how often it can be transferred.

I have not run into the reactivation issue using volume licenses, even going between AMD and Intel processor architectures. That licensing is what you should pursue if you need to have your VMs be portable between systems.

Good Luck

and also technically if using vMotion or DRS you may want to check what Microsoft licensing model you have, because technically you'll need a license for every HOST you vmotion to in the farm. So if you have three ESX hosts in your VMware Cluster, a VM could be on one of three hosts = 3 Microsoft Server licenses.

It can be beneficial to license with the datacenter edition.

a good article here to read through, although Microsoft have moved the License Calculators.

http://www.b3rg.nl/blog/blog-it/microsoft-server-2008-licensing-and-virtual-environments.html

Also read up about EVC - Enhanced VMotion Compatibility.  No need to license each host in a VMware cluster either.