Choosing a client for desktop virtualisation
Which one suits where?
Many organisations will assume that a virtualised desktop is best delivered on a thin client device. However there’s a good case for reusing existing PCs, and not all thin clients are created equal. How should you determine the best client device for your desktop virtualisation solution?
There are three main styles of client that you can use to support a desktop virtualisation initiative: thin clients, ‘zero’ clients, and fat clients.
Anyone who has been in the computing industry longer than ten minutes will recall that thin clients are far from new. Vendors were all abuzz about low-powered client devices in the early nineties, when a relatively new concept called HTTP had rekindled interest in centralised applications (back then, they called it ‘network computing’).
Thin clients still maintain a relatively heavy computing resource at the client side. You might not want to run SETI@Home on one, but they still have CPUs that would put an old ZX Spectrum to shame, and enough RAM to choke a cow. Wyse’s V90LE can accommodate up to 2Gb of Flash/1Gb of RAM.
Now, as in the early nineties, this gives IT departments significant wiggle room when it comes to balancing computational load between the server and the client, especially for apps that require some heavy lifting for user interfaces heavy in Ajax coding, for example.
For those that want to truly centralise their resources, however, zero clients are an alternative option. Whereas thin clients have an operating systems, these emaciated beasts do not. They have little more than a kernel, with enough code to kick everything (including system drivers) back to the server.
Marketing types will still try to move the boundaries of what constitutes a zero client. Watch for other terms, including ultra-thin clients. Pano offers the Pano Cube, a true zero client system with no memory, and no operating system. Wyse’s P20 zero client has no operating system, although it still contains 128Mb of local memory. both of them claim 3-3.5k watts of power usage - far less than even the leanest thin client, with an operating system to support.
But there is also a third option for companies considering desktop virtualisation, and that is to maintain a fat client architecture, at least for a while. Using traditional PCs for desktop virtualisation brings some traditional disadvantage, notably power usage. A laptop PC is still going to draw around 45 watts.
However, there are some benefits. For one thing, it can help to reduce the capital expenditure on desktop virtualisation if you maintain an existing arsenal of client PCs, because even thin clients cost money to buy. And ageing desktop PCs with low specs can use Microsoft’s Thin PC product – essentially a stripped-down version of Windows 7 with very lightweight requirements that allows the PC to act as a thin client.
Kingston University’s technical analyst Dan Bolton explains that when it virtualised its desktops, the University chose to use thin clients mainly for kiosks and print stations, while trying to keep as many of its traditional PCs humming along as possible using a ‘thin on fat’ architecture.
Kingston used VDI Blaster, a software program from Devon IT, to convert Windows PCs into thin clients that booted into Devon’s Terminal Operating System (DeTOS). This enables the machines to be managed using the firm’s Echo Thin Client Management Software.
“Academics can use their own laptops, and for non-academics, we'll repurpose workstations,” he says. He is hoping that the low computational overhead on the desktop PCs will enable him to skip a refresh cycle on at least some of them. “We’re expecting 5-6 years, but working on the basis of 3-4,” he says of PC lifetimes. At around £500 per desktop, that’s a big issue.
Sometimes, users take time to appreciate the value of a virtualised desktop versus the full richness of the PC or laptop they have been used to. Sean Whetstone, CIO at Reed Business Recruitment, says that there are 100-200 remaining diehard users that refused to buy into his desktop virtualisation programme and insist on using their laptops.
In practice, they’re effectively running as pure thin-on-fat clients, he points out. “You always have the person who says ‘I’m different, I'm a road warrior’. The reality is often that it isn't always true,” he says. ‘Maybe they need to read content, but 3G is very good now, WiFi in trains is very good in airports, so there's very few places where you're offline.”
When his users - with fat clients or otherwise - are offline, he gives them an encrypted memory stick to store files, along with a Microsoft Word or Excel viewer to review that content offline.
“If we look at the percentages, maybe we have given out a handful of these encrypted memory devices. We accept that we won't be able to get a signal everywhere.” In practice, very few use it.
Of course, there is likely to be a place for full-blown PCs in many organisations alongside virtualised desktops and in practice it’s likely that a mix of thin client devices, repurposed older PCs, and rich PCs or laptops with a locally-installed operating system will be required. ®