Microsoft Hyper-V

Hyper-V architecture

Hyper-V architecture

Technology overview

Microsoft Hyper-V, codenamed Viridian, previously known as Windows Server Virtualization, is a native hypervisor running on Windows 64-bit platforms, starting from Windows Server 2008. Hyper-V in Windows and Windows Server can replace older hardware virtualization products, such as Microsoft Virtual PC, Microsoft Virtual Server, and Windows Virtual PC, while providing more secure virtual environment with more features available.

Hyper-V architecture

Hyper-V architecture uses logical units of isolation called partitions (see the image above for more details). Partition is where parent (host) and child (guest) virtual machines are running.

Parent partition has direct access to physical devices; child partitions make use of virtualized devices, thus making themselves mostly independent of actual physical architecture.

Virtual devices can also take advantage of a Windows Server Virtualization feature, named Enlightened I/O, for storage, networking and graphics subsystems, among others. Enlightened I/O is specialized virtualization-aware implementation of high level communication protocols like SCSI to take advantage of VMBus directly, that allows bypassing any device emulation layer. This makes the communication more efficient, but requires the guest OS to support Enlightened I/O.

Note: Windows Vista (and matching Windows Server platform) and later, Linux versions using kernels 3.4 and newer, as well as FreeBSD can make use of Enlightened I/O, thus running significantly faster in most cases.

Guest platforms supported by Hyper-V

At the moment of writing this article, the below OSes are supported by Hyper-V platform:

  • Linux distributions: Ubuntu, Debiam, Red Hat/CentOS, SUSE, Oracle Linux
  • FreeBSD
  • Windows Vista SP2 and newer client Windows versions
  • Windows Server 2008 and newer Windows Server versions

Please refer to corresponding official Hyper-V Microsoft reference for detailed and most up-to-date version of the above list.

Problems and restrictions of Hyper-V

There are several known limitations of Hyper-V, some of them listed below:

  • audio hardware isn’t virtualized; there are workarounds, though
  • optical drives can only be accessed in read-only mode from guests
  • for certain CPU types, installation of WDDM graphics accelerators results in dramatic performance drop for guests
  • VM live migration (transferring across physical hosts without stopping the VM) is in most cases impossible

Note that new features are released for Hyper-V every year, and mentioned limitations might already be lifted in the latest Hyper-V release.

Monitoring Hyper-V with IPHost Network Monitor

IPHost Network Monitor offers, in Virtual Machines templates category, a number of templates capable of watching the state of both host and guest OSes of Hyper-V enabled system. IPHost can also be installed within guest Windows OSes, thus allowing to monitor its internal state parameters and services.