Virtualising the desktop

Everyone wants to escape the horror of rising energy costs. So why not run fewer servers?

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The no-brainer benefit of server virtualisation and consolidation is the reduction in energy costs, which is already saving forward-looking companies big bucks in kilowatt hours of electricity, not to mention in hardware and server administration.

No wonder so many enterprises are eying fresh virtualisation territory: the humble desktop.

You don't have to be a genius to realise that collapsing a dozen desktop systems with 500-watt power supplies into a single server with a 2000-watt power supply saves power and cooling costs. It's also obvious that collapsing a few hundred workstations into just a few physical servers would slash the power bill much further, while reducing the overhead of desktop system repairs and replacement parts. With cheap desktop terminals, total power consumption per seat drops dramatically, as does the heat generated by hardware, resulting in lower air conditioning costs.

This idea isn't new. Thin clients coupled with Citrix and Microsoft Terminal Services have provided the traditional method of pushing desktop sessions from the back office to the front room, but those solutions don't fit everywhere. Application incompatibilities abound and the relative fragility of a single Windows server instance running dozens of desktop sessions has always been a concern.

Hence the sudden proliferation of virtual desktop infrastructure (VDI) solutions. Riding the virtualisation wave, everybody and his brother are offering VDI products that deliver a full desktop (or virtual system) to a thin client. "We're seeing customers who really want to move away from terminal services for application incompatibility issues, among other things, and this is a clear alternative," says Mason Uyeda, Sun Microsystems marketing manager for desktop virtualisation. "VDI is like putting gasoline on the virtualisation fire."

VDI report card

The basics of these solutions are very similar. A thin client boots on the network and makes a connection to a desktop session broker. This broker is a piece of middleware that handles session requests on one side and pairs that request with an available virtual system. The details of how this works vary greatly from vendor to vendor, with some offering SSL connections from the client, while others do not. Protocol support to the desktop session is generally Microsoft's Remote Display Protocol (RDP) or Citrix's Independent Computing Architecture (ICA ).

VDI changes the way sessions are delivered to the clients. Rather than a single system hosting multiple sessions on a single OS, each client connects to a separate, independent virtual system running under VMware, VirtualIron or some other hypervisor. In this way, each system is isolated from the others and feels just like a "real" desktop.

This VDI approach has numerous benefits, beginning with almost complete application compatibility, because single-user applications don't need to be modified to run in a multiuser environment. Moreover, desktop isolation means that problems arising in a single desktop instance do not affect other instances and that virtual desktop systems can be automatically built from templates as the need arises. Furthermore, desktop VMs can be pooled; when VMs are combined with Windows roaming profiles, it doesn't matter what VM a user connects to because they're all the same.

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