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Virtual Desktops Are For Real  

By Randy George November 07, 2009 

After testing virtual desktop infrastructure software from nine vendors, we've got a solid feel for where VDI fits into your long-term strategy for end-user computing. The players in our review ran the gamut from smaller vendors that primarily act as connection brokers to brand-name server virtualization players. We tested products from Citrix, Ericom, Leostream, MokaFive, Quest Software, Sun Microsystems (since acquired by Oracle), Sychron, Virtual Iron (also acquired by Oracle) and VMware.  

We had three goals for our tests: to review feature sets, to develop a rudimentary cost/benefit analysis, and to determine whether VDI is ready for wide use. To that end, we tested each product using a broad set of criteria, including hypervisor support, manageability, resource management, provisioning, desktop access, performance, and cost. To test the software, we built a lab environment around a simulated business with 100 employees and four sites. (For more about our lab setup, see the box.)  

The Highlights  

Citrix's XenDesktop gets our pick for Editor's Choice for a comprehensive feature set, especially compared with the version of VMware's View that we tested in the lab. However, a subsequent version of View that came out after our test puts that product on nearly equal footing with XenDesktop.  

There were several outstanding vendors in other categories as well. For example, the award for the most robust back-end hypervisor support goes to Ericom. Ericom was the only vendor besides Citrix with full support for XenServer. While other brokers in our Rolling Review were able to serve out desktops running on Xen, only Ericom and Citrix were able to fully manage and provision virtual desktops. In addition, Ericom supports another dozen or so hypervisors, including some pretty obscure ones, so if you need to serve out virtual desktops across a wide range of hypervisors, give Ericom a look.  

Sychron and Quest are at the top of our list in the resource management area. Sychron OnDemand Desktop impressed us with its ability group virtual desktops into "habitats" and apply specific quality-of-service parameters to those habitats. For example, if your back-end hypervisor box is running low on resources, with OnDemand desktop you can ensure that users in the sales group are allocated memory and processing resources ahead of the HR group.  

Sychron also does a good job managing demand for desktops. Administrators can instruct OnDemand Desktop to automatically provision additional virtual desktops if the amount of available desktops in a given pool runs low. Those desktops can then be automatically spun up for quick access by users, as opposed to waiting 30 seconds for the virtual machine to boot from scratch. When user demand subsides, those virtual desktops can be automatically spun down to recover server resources. 

Quest also shines in resource management, and adds some load balancing features that Sychron doesn't have. An example is Quest's workload evaluator, which loosely resembles a software-based Citrix NetScaler appliance. As applications or terminal services sessions are launched within a virtual desktop, the workload evaluator decides which vWorkspace server should execute the connection based on existing CPU load, disk I/O, and user session count. If you're deploying VDI in a large environment, and load balancing is important to you, look at Quest closely as your connection broker of choice.  

For quick provisioning of virtual desktops, it's a toss-up between Ericom and Quest, with Sychron close behind. While all of the vendors in our Rolling Review can automatically batch-provision any number of virtual desktops, only Ericom and Quest handled the task of SID regeneration and domain addition quickly and painlessly. 

A few vendors are strong in desktop access. Citrix certainly has a built-in advantage with its experience in terminal services and application, and it shows in XenDesktop. Citrix can aggregate and serve out a vast array of applications, data, and system resources.  

Ericom was also impressive in this area. We found Ericom surprisingly robust at aggregating many information sources onto a single Web-enabled interface controlled by an Active Directory login ID. Whether it's a virtual desktop, a terminal services application, a private intranet, an Excel spreadsheet, or even an AS/400 connection to a legacy application, the Ericom Web Portal can broker and provide access to all these resources and more. We'd even go so far as to say that Ericom WebConnect can realistically replace Citrix in situations that only require a broker for access to back-end systems and applications.  

Lab Topology  

Our lab was set up as a hub-and-spoke network with four geographically disbursed sites. All of the three spoke sites were connected to the hub by a single T1 line. To maximize the bandwidth to each spoke site, we configured the hub's link with three bonded T1s, for an aggregate of 4.5 Mbps of bandwidth at the hub. Our fictional firm, Bits & Bytes LLC, consisted of 25 staff attorneys and 75 paralegals. To cut down on the risk of data loss via laptop theft, all paralegals were provided thin clients for access to their virtual machines. All staff attorneys were provided laptops with built-in EV-DO cards to get access to the Internet, and their virtual desktops, while traveling.  

The premise for testing using EV-DO for remote access was simple: if our users had a smooth experience over a 300-Kbps (or faster) connection, then network latency concerns would be generally be a nonissue when determining whether VDI was a viable platform for remote access to virtual desktops  

When it came to performance, there wasn't a significant difference among the vendors in our Rolling Review. Our test results dispelled a key concern we had with VDI: the impact of latency on the user experience. Across the board, virtual desktop sessions performed well with ping times ranging up to 200 to 300 milliseconds. Past that point, screen refresh times began to affect usability, but, thankfully, latency that high is usually only seen over dial-up connections.  

We found two factors that contribute to lightning-fast virtual desktop access. The first, obviously, is to allocate as much processing and memory to the back-end hypervisor as possible, especially if you're driving beefy client server apps within your virtual desktops. The second is to ensure that your virtual desktops are spun up before user access. Nothing will derail the success of your VDI deployment faster than users complaining that it takes an entire minute just to log in because a virtual desktop had to be produced from scratch.  

From a hardware resource perspective, it's not realistic to keep thousands of virtual desktops on hand at all times. Fortunately, all of the connection brokers we tested can help you find a happy medium through their ability to prepare more desktops based on connection load 

Wave Of The Future Or Another Fad?  

Server virtualization is one of the few technologies that have managed to live up to its hype. Can its virtual desktop cousin do the same, or is VDI destined to fizzle out like a wet firecracker? Our forecast says VDI has a good future in enterprise IT. Here are our reasons why.  

First, when a user calls the help desk with a laptop toasted by spyware, you can count on at least a couple of hours working on recovery, if it's even possible. With VDI, a machine infested with malware can be made to vanish and reappear faster than an end user can say "abracadabra." Assuming roaming profiles are available, the complete user environment can be restored right away. As a result, IT stands to gain significant time-savings in supporting the user population. 

Other improvements include easier upgrades of applications and operating systems for end users. No need to push a thousand copies of a new app or OS over the network. Simply create a new set of master images, and your users will find it served up hot and fresh the next time they access their machine.  

Second, VDI overcomes some limitations with terminal services. Terminal services offer similar opportunities for improved desktop management, but some legacy applications don't work well in a terminal services environment. Virtual desktops give you a robust option here. By sandboxing the application within the virtual desktop, you can deploy the legacy application on the platform for which it was designed to run without impacting your existing terminal server environment.  

Another issue is that terminal services often don't support customized desktops, a chief complaint of many people exposed to the technology for the first time. VDI solves this issue. 

Finally, your organization can more easily support multiple operating systems for end users in a VDI environment. Want to expose your users to Windows 7 in a controlled way? Serve 'em a virtual desktop. Want to prove to your CTO that Ubuntu Linux lacks the driver support required to be a viable desktop OS alternative? Don't just tell him, serve him a virtual desktop and show him. 

VDI Caveats  

The benefits of VDI are indisputable. However, while VDI is a sound technical solution for some serious IT issues, it's not the only solution. Many environments can get by using a combination of presentation and application virtualization, so we can't honestly say that VDI will be a game changer on par with server virtualization.  

And beware of vendors touting the savings you'll realize by virtualizing desktops, because there are plenty of hidden costs. First, you'll need serious server hardware to hand out virtual desktops, and you better have plenty of storage, too. Then there's the hypervisor and VDI broker licensing costs to consider. Vendors sometimes hype the fact that with VDI you can deploy thin clients as a replacement for more expensive fat-client machines to save on hardware costs. But last we checked, a decent thin-client machine is just as expensive as a low-end desktop/laptop PC. If your plan is to deploy $200 netbooks as a replacement for $1,000 business laptops going forward, then you're sure to reap significant savings, but most organizations aren't ready for that step.  

The result? The net cash savings that you thought you'd see from VDI might be more difficult to realize than you think. A better approach is to roll out a VDI trial to a select group and prove its efficacy. If VDI meets a need, budget dollars will follow.  

Even with those caveats in mind, we believe VDI will have a place in the enterprise in one form or another. Within the next decade, it's possible most organizations will subscribe to cloud-based virtual desktops running a thin OS hosted on a supercomputer running in a faraway land. Cloud computing, cloud storage, virtual desktops, and massively virtualized infrastructures are converging, and that convergence will change the way we deliver the desktop. It's just a question of when.