For too long, VDI has been seen as the next era in desktop delivery. This attribution implicitly presumes that VDI is to be the panacea for how all desktops are to be provisioned for their users.
Today's thinking is slowly shifting from that belief. First and foremost is the recognition that different use cases have very different requirements, not all of which are solved by virtualizing your desktops and throwing them into the data center. Although some businesses indeed jumped on VDI's bandwagon as early adopters, signs appear to indicate its rate of adoption is slowing. Qualifying that statement, smart businesses recognize that VDI's adoption makes sense for the special cases where it best fits—rather than being everything for everyone.
Rare is the company that has moved its entire employee base off physical computers and onto VDI. One reason for that stagnation could relate to the mismatch between the needs of IT and its users, which the previous article explored. Why do many VDI projects still remain in the pilot phase? A potential explanation is that implementing it to the wrong use cases introduces a set of big failures. What are those failures?
The irrationally exuberant might loudly proclaim that, "We'll be moving all of our users to VDI in this project!" Yet that same individual might not realize that inside most companies exists a range of user classes. Consider the following example classes that might exist inside your environment:
It should be plainly obvious that these different sets of individuals are best serviced through very different desktop delivery mechanisms. Although task workers, outside consultants, conference room workers, and labs might all present a perfect fit for VDI's desktop provisioning model, the absoluteness of VDI's efficacy grows hazy as one analyzes the other use cases.
Is it better to give the never‐in‐the‐office worker a VDI desktop or allow them to work with their uncontrolled home computer? Will a VDI desktop help the sometimes‐in‐the‐office worker while they're at their desk but significantly impede their activities once they leave?
Can the advanced requirements of knowledge workers and software developers be met by VDI's everything‐for‐everyone delivery model?
If your answers to those questions have you concerned, know that you're on the right track. VDI's entire delivery approach is well‐suited to a particular set of use cases. Individuals with LAN‐speed connections, limited need for customization, relatively static application sets, low resource requirements, and a rare requirement for access outside the office all represent round pegs for VDI's round hole.
However, there are use cases where even today's VDI technology advances can still lead to failure. The following list highlights the biggest five to watch out for.
Protocols like RDP and ICA are designed to be exceptionally bandwidth tolerant. One can run RDP or ICA through extremely narrow network connections and expect an acceptable user experience.
These protocols, however, also tend to be latency intolerant. The reason relates to the types of activities being done in the session. Clicking a mouse, entering text into a document, or moving a window works very well when latency is effectively zero. That same experience becomes very dissociative when latency grows above 200 or 300 milliseconds. Even with caching technologies, that extra fifth or third of a second between action and reaction usually makes for an unacceptable user experience.
VDI gains its cost efficiencies by collocating many virtual machines atop a smaller number of hosts. It rewards smart administration when more users work atop less hardware. Yet those benefits quickly unravel once "heavy" applications are provisioned to desktops.
These heavy applications—Adobe Flash et al, multimedia, CAD/CAM, imaging, and so on— consume comparatively larger quantities of system resources than do their lighter brethren. More still equals more, even considering today's advancements in resource optimization. Thus, supporting heavy applications incurs a comparatively greater cost per provisioned desktop than in the lightweight model.
Communication technologies that bring people together for live conversations require low latency if those conversations will have value. If you've ever placed a call over a satellite phone or poor VoIP connection and heard the multi‐second delay between speaking and hearing, you recognize the special challenge network latency creates for these applications.
At issue is not necessarily the technologies that enable these communication mediums to work within VDI. Vendors today are making great strides in caching and other technologies that limit the impact. A much more operational issue is the dynamics of the environment itself. Although 20 virtual desktops on the same host might see their communication platforms perform flawlessly, that same experience can quickly degrade when hardware resources go into contention.
Vendors today have also created mature technologies for rapidly deploying applications to VDI desktops. The process is little different than with physical computers. The sometimes unrecognized hurdle is that every application automation solution first requires prepackaged applications. That packaging process takes time and costs money.
The cost/benefit analysis gets worse when applications are not commonly used. Consider the one‐off situation where a single (perhaps homegrown) application is needed by one or a few users. Here, the effort to package can far outweigh just simply installing it via Next, Next, Finish.
Automation grows even less effective when such applications require regular updates. Manual installations don't fit into the VDI approach due to the fact that logged out desktops are typically cleansed and returned to an available pool. In essence, you would need to continually Next, Next, Finish any needed application at every logon. Not good. Creating special cases for one‐off users and their applications impacts VDI's cost model as well as its administrative optimizations.
Not every user in a business accomplishes their tasks as they sit at their desks or are attached to a high‐speed network connection. Some work in client or partner sites where connectivity isn't permitted. Others travel to places where connectivity is unavailable at worst and spotty at best.
Traditional VDI's solution to offline use often involves a check‐in/check‐out process whereby a virtual machine is transferred from the data center to the user's laptop. The sheer size of most virtual machines makes this a lengthy process. How much time did your last 40‐plus‐gigabyte file transfer require? More time than patience, one supposes.
Like so much in life, it seems that a focus on either of the opposing options outlined thus far suggests the real solution lies somewhere in the middle. Whatever product filled that gap would enjoy all the centralization functionality gained by storing desktop images in the data center as well as the flexibility of processing those images on local hardware. The final article in this series discusses how one approach, hybrid desktop virtualization, helps align these two needs under a potential single solution.