Up until yesterday, if you wanted to be the best boy of the class, you would have to license your virtual Windows and a number of well known applications (SQL, Exchange, SharePoint, and others) for each host the Virtual Machine could possibly land on. So, if you have a ESX cluster of 16 hosts and have one Windows SharePoint server that could be VMotioned to each of those 16 hosts, you would have to license Windows and SharePoint 16 times !!!!
Fortunately, Microsoft just announced that they changed this policy. Beginning Sept. 1, 2008, customers will be able to move any of 41 Microsoft server applications between servers within a server farm as often as necessary without paying additional licensing fees, and they can take advantage of expanded specialized technical support.
(EDIT: After reading Rich’s blog, it seems that the Windows OS is not part of this new license and therefore still requires a license for each host it moves to.)
Microsoft is also offering specialized technical support for 31 server applications running on a hypervisor validated by the “Server Validation Program“. Today the following Hypervisors have already been validated:
Cisco Systems, Inc.
Citrix Systems, Inc.
Virtual Iron Software
Now its time for VMware to get ESX validated, come on VMware !!!
(Edit: According to this article, VMware has already signed up)