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Desktop virtualisation With the economy looking a little rosier, companies are coming round to upgrades that have been on hold for longer than usual. As they refresh the corporate desktop, should they be looking at desktop virtualisation too?

Mark Bowker, analyst at Enterprise Strategy Group, thinks IT decision-makers can minimise headaches and maximise gains by tackling their desktop refresh and virtualisation in tandem. “The two projects should be considered together. Companies should at least be having that discussion, and ultimately could find that desktop virtualisation streamlines the whole Windows 7 migration,” he says.

Server-side virtual machines are unable to make use of specialised hardware at the client level

Windows Server 2008 R2 includes a radical overhaul of the Terminal Services technology in previous versions. The new version, called Remote Desktop Services, is offered as a specific server role to offer access to specific applications, or to a whole Windows desktop, either from within the corporate network or over the internet.

Services within this role include a connection broker that manages load balancing and automatic session reconnection to help optimise server performance. There is also a virtualisation host that integrates with Microsoft's Hyper-V hypervisor, either providing a personal virtual desktop to each user or offering shared access to a pool of virtual desktops.

There are also several features in the Remote Desktop Client software that connect to Windows Server and that light up only when used on Windows 7. Among security features, the Remote Desktop Gateway service can be configured to authenticate and authorise a client in the background after a configured session timeout is reached, without disturbing the user. It can also update clients with the latest software patches when in a virtualisation session.

Other goodies include support for multiple monitors (up to 16) and bitmap acceleration to improve the display of graphics-intensive applications. Heavy users of audio can also benefit from device redirection, so that they can send the sound input device on the client to the virtual desktop. This comes in handy for voice recognition and audio recording.

One of the features in Windows Server 2008 that make desktop virtualisation easier is RemoteFX from Calista, a company Microsoft acquired in January 2008. “It’s about making the client as easy to use as possible,” says Ian Moulster, a product manager at Microsoft who specializes in desktop virtualisation.

RemoteFX was included as part of Remote Desktop Services in Windows Server 2008 R1 SP1 and Windows 7 SP1. “It virtualises graphics cards at the server end, allowing virtual machines to share and make use of the graphics processor,” says Moulster.

Typically, server-side virtual machines are unable to make use of specialised hardware at the client level. This can be problematic for companies with graphics requirements, for example in areas such as computer-aided design or in academic applications where data visualisation is key.

Moulster adds that the technology also leads to computational efficiencies in the server room because the server hardware doesn’t have to work as hard to emulate graphics performance as required by desktop applications. “RemoteFX lets you take the load off the CPU at the server end and gives you a slicker front-end interface,” he says.

Other advantages include dynamic memory. In the past, IT administrators have had to allocate a specific amount of RAM for each virtual machine that they instantiate. This can make management burdensome for them when the number of virtual machines rises sharply as more users come online. Many employees may require more than one virtual machine for different purposes, leading to “virtual sprawl”.

Dynamic memory allows an administrator to set a nominal level of memory for a virtual machine and then use the hypervisor to allocate memory dynamically as it runs, according to computational demand.

This can produce significant memory savings and therefore a reduction in upfront capital expenditure, Moulster says. He adds that companies normally allocate about 1Gb of memory for Windows 7 when not using dynamic memory, which may be a waste. “In tests, we found that when you allocate a nominal 512Mb of RAM most of the virtual machines averaged out at 750Mb of RAM,” he explains. “That gives you a 40 per cent increase in the density of the virtual machines that can run on the server, improving cost effectiveness.”

No matter what desktop operating system you end up using, it may be worth considering some form of virtual desktop integration or application virtualisation at the server level as you roll out a new desktop environment. But be sure to size the server accordingly, and be prepared to make capital investments in the data centre to support the increased load. For optimal results, you may need to allocate some IT budget at both ends of the LAN. ®

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