Large PC users are increasingly looking to VDI - virtual desktop infrastructure, which uses VMware to host virtual PCs - as an alternative to current server-based computing approaches such as Citrix and Windows Terminal Server (WTS), says thin client developer Igel Technology.

Igel has added VDI support to its thin clients and also to a PC conversion card, which it claimed allows old PCs to be redeployed as diskless workstations. The supplier said this means that customers can deploy virtual PCs to the desktop for as little as £162 a user - or £95 if reusing an old PC.

"The interest in VDI is across the board. Companies are looking at it as an alternative route to server-based computing that gives you the best of both worlds," said Stephen Yeo, Igel's worldwide strategic marketing director.

As we have reported in the past, VDI uses VMware servers to host virtual PCs. Each user therefore gets his or her own virtual system, instead of sharing a single multi-user PC as they would with Citrix or WTS.

As with Citrix, say, VDI enables users to run applications or an operating system that cannot run on their desktop device, as the desktop is merely the local display for a remote PC.

"To connect a thin client into the VMware infrastructure you need a connection broker, then when you log in it goes off and finds you a virtual PC," Yeo said. "Most of our customers are asking for the Leostream client, so we've embedded that. We are working on others."

He explained that a normal PC would either download the connection broker client dynamically or connect to VDI via a web-browser, but with a thin client the VDI software needs to be embedded instead.

That is also where the PC conversion card comes in, embedding thin client software into what was a standard desktop system, he said.

"If you've got old PCs, the temptation is to use them as Citrix or WTS clients and keep the local hard disk and operating system, but then they're still vulnerable to viruses and still need management," he added. "Our PC conversion cards replace the hard disk with a Linux client in flash memory, with all our client services built in, such as IP phone support."

Comparing the VDI approach with Citrix or WTS, Yeo said that VDI is more flexible, as users can change the configuration of their virtual PC, yet it is still manageable.

"You can move VPCs around more easily than you can move Citrix servers, and it's robust because a catastrophic software event only takes down that VPC," he added.

"If a customer already has non-OEM licences for Windows XP, they can re-use those on VMWare. In Citrix or WTS they'd need a CAL (client access licence) too, " he continued. "You do have to pay for VMware though."

On the other hand, he said that virtual PCs still need security software running in each virtual machine, whereas in Citrix it's centralised, and each virtual PC consumes more server hardware resources than a Citrix session.