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.

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.

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.