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With Andy Rooney off the air, the world has lost one of its most prolific spouts of curmudgeonry. Hopefully I can make up for that a little.

Over the past two years, one of the biggest buzz-phrases in the IT industry has been “desktop virtualization” or “virtual desktop infrastructure (VDI).” All of the major virtualization vendors have VDI products and have been pushing them heavily (and fairly successfully) since server virtualization got IT departments and business users comfortable with the idea of virtualization in general.

I get a lot of questions about desktop virtualization. Mainly, companies want to know if the technology is a good fit for their infrastructure. My go to response has become “maybe, but probably not.” As with most buzzy things, VDI is surrounded by a lot of hype and false promises.

What is VDI?

Although it’s dressed in new language and there is certainly a lot of new technology involved, VDI is built upon the same centralized services model that’s been around for decades with mainframe infrastructure. Anyone who’s ever used a “green screen” Unix terminal or Microsoft Terminal Services has experienced the basic premise behind VDI. Both of those older technologies are known as session virtualization.

In session virtualization, a remote user is provided a view and input capability to a server located in the datacenter. The only work that the local PC or thin-client is doing is transmitting keystrokes and screenshots back and forth across the network. Each session is served up from a shared server (virtual or physical) and changes to that server can affect everyone who is logged in.

VDI takes that same concept a bit further and gives each user their own virtual computer hosted from the data center. Instead of sharing an operating system with many other users, they have a complete environment to themselves, albeit, they are sharing physical resources. This approach has several benefits, in particular it provides another level of granular control and fault isolation. Virtual desktops can be moved around between different physical servers and can be easily copied, destroyed, etc.

One of VDI’s strengths versus session virtualization is that it provides the ability to “check out” a virtual desktop, meaning mobile users can continue working without being connected to the network. The VDI client being used slurps down a copy of the virtual desktop from the central server and then syncs everything back up when the user is back in the office. In practice, it’s slightly more kludgy, but that’s the basic idea.

With VDI, as with session virtualization, it doesn’t really matter what hardware is issued to the end user. Many companies issue thin client terminals that aren’t much more advanced than a fancy calculator. Others have used VDI to implement ”Bring Your Own Computer” policies. They provide employees with a technology allowance to purchase a laptop of their choice and install a VDI client to provide access to company resources via a virtual desktop, thus bending to the consumerization of IT.

So I Thought You Said Desktop Virtualization Was Bad?

Well, no. I didn’t say it was bad. I just said it was likely not a good fit for most organizations. While there is some really neat technology involved that allows for a lot of new approaches to delivering services to end users, VDI has some serious draw backs to consider. Chief among those is complexity.

Complexity is something I try to steer clients away from and VDI is the epitome of complex. If your IT department is already comfortable with managing multiple storage appliances, fiber networks, and virtual server farms with a proven up-time record, then you might be ready for VDI. However, a lot of the companies that I see pursuing VDI projects have just recently virtualized their servers and are green to the field. They’ve got virtualization fever.

In many cases, these same companies haven’t mastered providing simple services such as e-mail and connectivity. If your IT department struggles to keep the e-mail servers up and is talking about implementing VDI, call me, and I’ll come hit them across the hands with a ruler. When e-mail goes down, most people can continue working in some fashion. But when they can’t access their virtual desktop or any of their applications, it’s probably time to send everyone home for the day.

VDI and session virtualization can solve a lot of IT management problems but they both require a solid foundation. Many of the promises I’ve seen VDI salespeople make have been in regards to that foundation – that VDI would help shore-up or fix a broken infrastructure. That’s just not the case. Infrastructure needs to be rock-solid before VDI is even an option.

For businesses struggling with core services issues, I’d recommend focusing on getting those services working properly and then maybe testing out a session virtualization product like Microsoft Terminal Services. Session virtualization has been around for decades and is far simpler to implement and manage. There is a significant overlap between the session virtualization and VDI, so session virtualization could be used as a stepping stone to VDI in the future.

The complexity involved in providing a high-uptime VDI environment is more than most small-to-mid sized IT departments can handle without relying heavily on third-parties and incurring significant cost. As VDI scales, the cost/complexity/benefit ratios normalize and start to make sense, but on a small-to-medium scale it just doesn’t seem like a good idea, regardless of what the rep for VMWare or Citrix is saying.

Where does VDI fit?

I think there are two areas where VDI makes sense and they are at opposite ends of the spectrum. VDI is often a good fit for very large organizations who can leverage the virtualization infrastructure and skill-sets they already have. As a hosted service, VDI also seems to work out for very small organizations by giving them the benefits of big infrastructure without the hassles and cost.

The reasons that VDI works with these two groups has to do with scale. Hosted providers and enterprise IT departments can build VDI environments with the redundancy and resiliency required to deliver virtual desktops as a stable service. They can then provide those desktops to end users and customers at a reasonably low cost per user. With current technologies, it would be extremely difficult for a SMB organization to self-host virtual desktops with similar stability and cost.

As with all things, there are caveats. It would be foolish to say “VDI won’t work for your organization because you’re too small.” It could be that you have the right mix of staff and infrastructure to make it work. If so, I’m only saying that you’re probably an exception to the rule.

I think it’s important to recognize that VDI is not the shining savior of corporate IT that it’s being made out to be. The technology is solid and builds upon 30+ years of centralized services. There are a lot of benefits to VDI that extend past session virtualization and it can provide a lot of flexibility. But the current hype far out-stripes reality.  If vendors were more honest, I think they’d be presenting VDI as Advanced Terminal Services, because that’s really what it is.