Using free PC virtualisation tools

Microsoft’s tale
Like VMware, Microsoft has two server virtualisation products; one is a hosted application, the other a hypervisor. The hosted product is Windows Virtual Server 2005 which, as you might expect, requires Windows Server to run.

The R2 release includes 64-bit implementations, although you can’t host 64-bit virtual machines on Virtual Server 2005 and you can’t allocate more than one virtual processor per VM, despite support for symmetric multiprocessing hosts.

Management is via a web-based interface on a single server basis with the usual tools to create, start and stop VMs, take snapshots and so on. There is little scope for load balancing and definitely no support for live migration of virtual workloads. Indeed, much of the development effort in this area has gone into the hypervisor product, Hyper-V.

Microsoft Hyper-V is delivered as part of Windows Server 2008, including the Small Business Edition and is reliant on hardware drivers provided by Windows. However, a standalone Hyper-V Server is also available which includes Windows Server Core to support it. The Hyper-V Server product is free, but licences are needed for Windows running in host VMs whereas the Hyper-V in Windows Server 2008 will be licensed for one or more Windows VMs depending on the edition purchased.

A very scalable hypervisor, Hyper-V can host virtual machines running 32-bit and 64-bit versions of both Windows and Linux guest operating systems. Basic management tools are freely available, offering features similar to those in V irtual Server 2005.

Access to more comprehensive management facilities is provided through System Center Virtual Machine Manager 2008 (VMM2008). This can be used to manage both Virtual Server and Hyper-V platforms with support for dynamic resource allocation and migration of virtual workloads from one server to another (Hyper-V only). The current release of Hyper-V doesn’t allow for live migration but it is in the R2 release which should have shipped by the time you read this. VMM2008 can also manage Citrix Xenserver implementations (see below).

What you get from Citrix
Citrix has just one server virtualisation product ­ Xenserver, the commercial implementation of the Xen hypervisor technology also available in a number of Linux distros. The licence fee for the latest Xenserver 5 release was dropped in February.

Xenserver is a very scalable product with support for up to 32 processors and 128GB of memory on the host systems with guest VMs able to have up to eight virtual CPUs and 32GB of Ram each to run both 32-bit and 64-bit implementations of most Windows and Linux operating systems.

Citrix retains many of the more advanced features offered with the original licences including the ability to manage multiple host servers from the Windows-based Xencenter console plus live migration of virtual workloads. You also get integrated P2V (physical to virtual machine) and V2V (virtual to virtual machine) conversion tools and support for a wide range of back-end storage technologies.

To add dynamic provisioning of virtual machines, workflow automation, load balancing and high availability failover, you need to buy the one of the Citrix Essentials add-ons: Citrix Essentials for Xenserver or Hyper-V. Citrix and Microsoft have agreed to work together to develop management tools able to work with virtualisation products from both companies.

Inside VMware Workstation
With the exception of Microsoft’s Virtual PC 2007 and Sun’s Virtualbox, free virtualisation products to run on your local desktop PC are pretty rare. Market leader VMware refuses to ditch the price for its VMware Workstation. It argues that it delivers a lot more than virtualisation, such as tools to model network workloads, record and replay virtual machine sessions and debug applications running in them.

The built-in extras make VMware Workstation popular with its intended development/testing market which doesn’t mind paying for these facilities.

Meanwhile if you just want to run virtual machines VMware Player can be downloaded for free, although you will need VMware Workstation or another product to create the VMs in the first place.

This article was first published in June 2009.