Windows Server is Windows Server right?
Well not any more! Windows Server is now a bona fide virtualisation platform now that Windows Server 2008 R2 Service Pack 1 brings us a major enhancement to Hyper-V; Dynamic Memory.
Dynamic Memory is one of the final pieces of the hypervisor puzzle that Microsoft has had missing to date in comparison to other virtualisation platforms such as VMware.
VMware’s enterprise range of hypervisors have had the capability to over commit memory for some time, allowing virtual machines to “use” more memory than is physically available in the host physical server. This was achieved by letting a virtual machine believe it had more memory than it actually did and then allowing it to have access to more “actual” memory if it needed it with the total amount of memory that could be assigned to all guest VMs exceeding the actual physical amount of memory in the host, hence – over committing. Of course, if many VMs require lots of memory then limits are reached and limits are imposed by the hypervisor.
Dynamic Memory in Hyper-V SP1 (it’s available for all variants of Hyper-V including the stand alone Hyper-V Server 2008 freebie product) works in a slightly different way but ostensibly does the same thing by allowing virtual machines to have access to more memory on-demand with the total amount potentially committed to VMs being greater than the actual total available physical memory in the host.
As a provider of cloud and hosting services, we have been keenly watching SP1 and testing with pre-release version to help us to decide if it makes Hyper-V a good enough alternative to other virtualisation platforms for us to commit our technical direction to this route.
With the full release of SP1 we have committed to move our virtual environment from VMware to Hyper-V from April 2011 with all new hosts from MArch 2011 being deployed using either Windows Server 2008 or Windows Hyper-V Server.
Long term performance testing of Hyper-V with these new options will commence from this week, expect some reporting back once we have meaningful data to share.