Will Windows 7 spread desktop virtualisation?

Savings can be tricky to calculate

Further, Microsoft's Woodgate worries that companies can overestimate their potential cost savings with virtual desktops because they don't add the cost of gearing up the data centre to support it.

"You're replacing the hard drive of a laptop, which is about the cheapest memory there is, with space in a Storage Area Network, which is about the most expensive memory there is," Woodgate adds.

On that point, Woodgate and Winburn disagree. Server- or SAN-based storage is secure, backed up, cheaper to maintain and far more rarely lost, broken or abused than a laptop, Winburn says.

And, Thornton says, even looking just at hardware costs, virtual desktops saved his organization about $100 (£60) per machine. The district wound up using the free XenServer rather than VMware's vSphere on the servers as was the original plan.

"With a thin client and Linux OS on it, half a gig of RAM, a little Atom processor, licence for XenDesktop, plus the cost of a server divided by 30, we figured we could get 30 VMs per server, we came up with about $550 per unit," Thornton explains. "Compare that to $650 to $700 for a regular PC. Thin clients have no moving parts, they're built to resist heat. We figure they'll last eight or 10 years, compared to three or four Gartner recommends for a PC. That raises the savings even more."

In zeroing in on cost as a crucial element in the virtualisation decision process, Thornton and Winburn agree with the majority of IT shops. Indeed, Mann's survey at EMA showed that three quarters of companies interested in desktop virtualisation primarily wanted to save on hardware and administration costs, and half expected to save on software.

That contrasts with server-based desktop virtualisation, in which 70% of respondents said flexibility and agility, the ability to add or reduce computing power, the ability to launch as many "new" virtual PCs as necessary at a moment's notice and the ability to give users access to "their" PC image or files no matter where they work, was the main reason to switch.

Schools' big savings

As one of the fastest growing districts in the country, the Montgomery Independent School District standardised two of the three schools it opened this fall on Citrix virtual desktops. In addition to saving $100 per unit and more than doubling the lifespan of his PCs, Thornton says there were other savings. "To support the other 2,000 PCs in the district I have five people and they never get to sit down all day long. For the 700 [new virtual desktops] we have one person and he only works on it about an hour or two per day."

All of the district's 700 virtual desktops use XenDesktop on the client, connecting to XenServer servers on the back end. All but around 15% use shared session connections. The rest, mostly in computer labs and in classes that need to use Adobe Photoshop, computer assisted design software or other resource-intensive applications, have VDI setups that give them a dedicated virtual machine for additional power.

It's not just education in Texas that's tapping the power of virtualization. At the University of Texas Medical Branch, the support, hardware and network load are different depending on what type of virtual desktop is involved, Winburn says. But any kind of virtual desktop delivers a far more efficient use of IT resources than putting all the power of a PC on every user's desk, he explains.

"The big difference is that you don't have to support the endpoint, just the user settings and the network and servers," Winburn says. "I could put five or six PCs on a T1 at a clinic somewhere and people are going to complain that Outlook is slow to open, or it takes too long for browsing. I could throw 30 or 40 [Citrix thin clients] on that connection sharing one desktop image back in the data centre, and they run like a champ."

Desktop virtualisation options are expanding

Traditional, terminal services-based virtual desktops allow dozens or hundreds of end users to sign on to a single operating system and set of applications, all running on a backend server. That keeps costs very low, but limits or eliminates the ability of individual users to configure their own environments. It also keeps them from viewing bandwidth-intensive video, Flash animation or other multimedia, whether on the web or on controlled internal applications. This happens because most desktop virtualisation software doesn't have a mechanism to support it, Mann says.

That's changing with newer versions of the server software from both Citrix and Wyse. Citrix' recently released XenDesktop 4 supports not only multimedia, but also USB connections at the client side. The result is that end users can plug in peripherals like printers, scanners and memory sticks or even fans, lights and desktop toys if they like, Mann says.

VMware, long the leader in the virtual server market, plans to release similar support in its VMware View VDI products early in 2010.

But even then it will trail Citrix in the number of delivery methods it offers for virtual desktops and the breadth of products tailored to specific problems, like the Citrix branch repeater that slashes the amount of bandwidth required for remote sessions of the notoriously chatty Exchange server, Mann explains.

Further, Citrix' HPX technology eliminates one of the few barriers to using a virtual PC just like a real one, according to Graves. HPX allows users of VDI-based virtual desktops to use web-based multimedia and to plug USB devices into their local machines, even if the software operating the peripherals and the browser is running in a data centre somewhere, Graves says.

With that addition, the bank can expand its centralised virtual desktop support and delay buying new PCs, reducing the $400,000 (£250,000) it currently spends on new hardware, Graves says.

It's not clear yet whether the 10% of Independent Bank's 1,200 employees who don't already use virtual desktops will be able to make the leap to VDI, according to Ben Kohn, senior systems architect for the bank.

Kohn has been supervising the bank's tests of Citrix USB and multimedia support, connecting non-virtualised users to VDI-based virtual desktops. The tests have gone well and most users like being able to use the newest operating systems and the speed and power they get from a dedicated VM running on a bank server, rather than the same applications running on an aging PC.

Another benefit: Because the "desktop" each user accesses sits on a server in the data centre that IT patches and upgrades, end users have had fewer problems from viruses, malware and misconfigured applications, Kohn says.

If the bank ends up migrating those users permanently to VDI-based virtual desktops, they should continue to see top performance, because the bank upgrades servers faster than it would refresh PCs, Kohn explains. The decision about whether to migrate those users or more widely adopt the latest version of XenDesktop won't be made until its tests are complete, however, he says.

No rush to virtualise, with or without Windows 7

Given all the variables that are still up in the air, there probably won't be an explosion of Windows 7-inspired desktop virtualisation in Corporate America anytime soon, according to Michael Rose, client hardware analyst at IDC. Traditional shared session virtual desktops will remain popular in their traditional niches, whether with Windows 7 or other OSes, Rose says. It will take time, however, even for companies eager to use newer VDI systems to add the network and server capacity they require.

"It would involve significant spending in the data centre to accommodate adding vast numbers of users on virtual machines," he said. "Desktop virtualisation will continue largely to be a tactical technology, though as it moves more toward the endpoint device, handhelds and other nontraditional hardware, there's more of a possibility it will become very common."

Bottom line: Windows 7 could be a catalyst for some additional virtualisation, given improvements in the technology that have helped mitigate concerns over relative performance, perceived lack of personalisation and other issues. However, this technology isn't seamlessly stitched together yet. Administrators still have to master the nuances and best practices, and few will want to make the transition at the same time they convert over to Windows 7.