Weighing the pros/cons of desktop virtualization

A virtual desktop environment will present new challenges to those experienced with server virtualization, analysts say

Companies that have deployed virtual servers don't need to start from scratch for their desktop virtualization deployments, but there are a lot of new challenges to tackle.

Successful server virtualization deployments lead many IT managers to believe desktop virtualization would provide the same benefits. While that is partly true, companies need to be aware of how the two technologies differ, industry experts caution.

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"Desktop virtualization is a very different beast and should not be treated as simple enhancements to the server strategy," says Natalie Lambert, principal analyst at Forrester Research. "The drivers are entirely different and the environment will present new challenges to those experienced with server virtualization."

For instance, desktop virtualization doesn't offer the near-immediate cost benefits many cite with virtual server rollouts. And while virtual servers present new security and management challenges, many argue that in the desktop realm, virtualization improves security and manageability for IT departments. In addition, the sheer numbers involved can be strikingly different.

"IT managers could be taking on 500 virtual servers, and that is a lot, but it is nothing compared to 10,000 desktops," Lambert says.

According to industry experts and IT pros, there are some similarities and many differences between virtual servers and virtual desktops. (See related story, "No virtualization skills? Better get started.") Here we highlight key factors that could help avoid major headaches when moving virtualization to the desktop.

Complexity intensified

Most IT departments at enterprise companies have exponentially more desktops to support than servers, virtual or otherwise. The sheer volume of desktops should be one of the first criteria IT managers consider when making a move to a virtual platform.

With more than one billion PCs in the world, there's a huge opportunity for virtualization, but "all the requirements of the PC world need to be maintained as you migrate into the data center," says Mark Margevicius, vice president and research director at Gartner. "The desktop realm represents a lot more moving parts, considering all the uniqueness that happens on a PC needs to be maintained."

Server virtualization teams are unlikely to be responsible for the desktop infrastructure, beyond the servers that host the virtualization platforms. That means desktop groups need to rethink patch management, software distribution and other functions when applying them to a centralized system rather than a slew of disparate desktops.

"Desktop teams know how to manage 100,000 machines so the practices and policies are completely different. In the virtual realm the desktops come back to the server environment but cannot be thought of in the same terms," Forrester's Lambert says.

For Jake Seitz, expanding his company's VMware server virtualization deployment to include desktops was driven by compliance requirements and a move away from supporting desktop hardware. The enterprise architect at The First American Corp. in Santa Ana, Calif., says his group may be supporting less desktop hardware, but now they are responsible for maintaining "all these unique virtual machines." With 22,000 desktops, Seitz says the plan is to migrate 3,000 to 4,000 per year as hardware comes off its lease or as it fails – a plan that will help his team stay on top of the new virtual environment as well.

"The desktop has its own challenges, including the uniqueness of images personalized by end users. With a ‘patch once and push many' approach, the risk of breaking software goes up exponentially," Seitz says. "We have one-off machines in legal or finance, for instance, and we patch them ad hoc as needed. We realize we can't do desktops in a big bang move; it has to be an incremental move."

Double the cost, half the ROI

While server virtualization virtually guarantees a speedy ROI, desktop virtualization can be cost-prohibitive to start and deliver a somewhat less immediate and difficult-to-quantify return on the substantial investment.

Analysts estimate choosing virtual desktops can cost 150% to 250% more than traditional PCs — and that's just for the direct cost of acquiring the technology. Savvy IT managers realize when pricing out a project they need to also calculate indirect costs.

"Desktop virtualization is a lot like hybrid cars. No one disputes the value and they love the idea, but it is just too expensive to write a check and pay a lot when the traditional version is cheaper and already paid for," Gartner's Margevicius says.

Yet for some organizations the benefits are enough to warrant the investment. For Kevin Nolan, the potential cost, time and labor savings associated with virtual desktops is driving his organization to evaluate the technology. Nolan, manager of systems engineering at Mohawk Industries in Calhoun, Ga., says his company is expanding their use of virtualization technology beyond the 500 VMware virtual servers his group supports. Nolan, who will be speaking at this month's Network World IT Roadmap Atlanta, says adopting virtual desktops would enable his company to extend the refresh cycle on PCs.

"If you have a virtual desktop, you can stretch hardware for more like five or six years, rather than the standard three-year PC refresh cycle," Nolan says. "With a lot less hardware, there are a lot fewer opportunities to break and have to fix machines."

Considering the cost, Nolan says his desktop and server team are working together to evaluate several vendors, including VMware and Citrix. Nolan realizes the desktop realm requires expertise in managing multiple PCs, which Citrix has mastered, but because the technology will reside in the data center and involve the server group, VMware might be a better option.

Analysts say customers could realize price cuts if they did add desktop technology from their virtual server vendor. "Definitely, the more customers buy from one vendor, the more discounts they will receive and the lower the cost per seat could be," Forrester's Lambert says.

For John Turner, desktop virtualization isn't the right move yet. The director of networks and systems at Brandeis University in Waltham, Mass., says his group evaluated the possibility of extending their successful server virtualization implementation to the desktop and the argument didn't stand up. For one, being a university it would be a challenge to "lock down" a PC image for the majority of students, faculty and others to use. And without solid support for streaming video across the virtual PCs, Turner says he couldn't sign on just yet.

"From a university perspective, we have such a diversity of functions and we can't dictate too much to the end users. And without gigabit to the desktop, performance would be poor," he explains. "We imagined replacing only computers that fail, stretching the refresh cycle, going back to dumb terminals, but we have to also provide what people want with a powerful operating system."

First American's Seitz agrees that many virtual desktops need to be cloned from one golden image, with some changes applied depending on groups. But the majority of desktops incorporate "Microsoft Office and some basic functionality because that is all they need," he says. While First American is using VMware VDI primarily because it represented "the most cost-effective option," Seitz is also realizing benefits not directly related to costs.

"The number of help desk calls drops substantially because they related to hardware and we threw that out, and business continuity plans are more easily implemented," Seitz says. "Auditors are happier that our data doesn't leave our data centers and go overseas. The end user on a virtual desktop only sees a representation of the data and not the data itself, which simplifies a lot of what we do."

Don't forget network, storage

IT managers must also look closely at network and storage requirements in their virtual desktop environment because if they don't, what is already an expensive endeavor will become too costly to continue deploying.

"Typically when doing an ROI against desktops, you don't factor in network and storage costs. You need to break that all down in a per-virtual-machine model," Seitz says. "But storage could be a big cost; shared storage is not cheap."

Storage is a lesson already learned by server teams deploying virtualization, says Andi Mann, vice president of research at Enterprise Management Associates. For that reason, desktop groups should depend upon the experience of their peers when considering storage. For instance, 5,000 desktops each with a 60-gigabit drive built-in could prove to be cost exorbitant. But by bringing those storage requirements back to the data center, Mann says, via thin provisioning and data deduplication, desktop teams will lessen their costs and optimize resources.

"Storage management is one of the biggest concerns about desktop virtualization. A lot of resources can be wasted if not managed properly," Mann says.

He adds that the network is another area of concern, thought it's not typically on desktop managers' minds. While Gigabit Ethernet is a standard for data centers, it has yet to be widely deployed to the desktop.

Determining network capacity and understanding if an upgrade is in order could help IT managers decide on virtual desktops, Seitz says. "The network needs to be able to handle aggregate traffic from many desktops to one location in the data center, so an upgrade from 100MB Ethernet to Gigabit might be necessary," he says.

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