Microsoft first released its Hyper-V virtualization platform with Windows Server 2008, leading many people to assume that Hyper-V required the Server 2008 OS—essentially equating the product with Virtual Server 2005 and out of the ESX Server class. However, that has never been the case. Following the initial release of Hyper-V with Server 2008, Microsoft announced a standalone version of Hyper-V called Hyper-V Server 2008. Hyper-V Server 2008 is a free download (http://www.microsoft.com/downloads/details.aspx?FamilyId=6067CB24-06CC-483A-AF92-B919F699C3A0&displaylang=en) that doesn’t require Server 2008.
Table A summarizes the primary differences between Hyper-V Server 2008 and the version of Hyper-V that ships with Server 2008. Essentially, Hyper-V Server 2008 is oriented toward smaller businesses that haven’t adopted Server 2008. It provides the same levels of performance and the same guest support but is more limited in that it doesn’t provide support for more than four CPUs or more than 32GB of RAM. Also, it lacks enterprise-oriented features such as support for Failover Cluster and Quick Migration.
After reading about how the Hyper-V architecture uses the parent partition for device drivers, you might wonder how Hyper-V Server 2008 supports devices. Hyper-V Server still uses a minimal Windows Server installation in the parent partition that contains device drivers and a bare minimum of functionality, such as the capability to network and create a domain connection. But you can’t use it to create VMs because there’s no GUI and no commands for creating a VM. Although it might be theoretically possible to create VMs with WMI, in practice you must use a remote instance of the Hyper-V Manager to do so.