This is the first in a series comparing the strengths and weaknesses of virtualized desktops. The three main players in virtual desktop integration (VDI) are Citrix, VMWare and Microsoft. Because it was first in the game, Citrix is often cited as the main player. I’m first reviewing Citrix XEN Desktop, then VMWare’s Horizon View and finally Microsoft’s VDI. Virtual MachinesCitrix is often the first name invoked when someone’s considering a virtualized desktop solution. Though the company’s been around since 1989, the Citrix we know today got its start in 1995 with WinFrame, which delivered a multiuser platform for Windows NT 3.51. In 2007, Citrix purchased XenSource, which delivers a virtual desktop. Its VDI is different from WinFrame (now called XenApp) in that it delivered a complete, rather than a shared, desktop to users. One of the main advantages to this approach is it allows multiple images to reside on the host server, even for the same user. Citrix’s virtual desktop, XenDesktop, provides centralized control of client desktops and easier migration to a new desktop OS. Centralized control reduces the number of client desktop images that you need to manage and patch, as well as centralizes their location in the data center. Migration is made easier because you don't need to upgrade all your older physical systems in order to take advantage of a new client OS, such as Microsoft’s Windows 8. XenDesktop can run virtualized on a host like XenSever, VMWare or Microsoft. Or, it can run distributed across your organization’s infrastructure, meaning that you can install the desktop service on existing hardware and a broker can connect remote users right to their existing desktops. Why would you want to do that? Why not deliver the desktop in the office the way you would for users at home? One reason is that this approach allows the enterprise to leverage existing hardware. An organization with 1,000 users will need a robust back end in order to manage all those requests. For example, VDIs running a 64 bit OS will create huge pagefiles eating up enormous amounts of disk space on the XenServer. You don’t have that problem on physical PCs, which often have vast amounts of extra disk space. Using existing desktop PCs can also help you transition to a completely virtualized environment. The hardware is already in place with generous amounts of disk space, the PCs already have their apps and employees have all their settings. All the PC needs is the client piece and it’s ready to go. (Of course you need to build the back end.) Using existing desktops isn’t perfect. If the physical machine is turned off or hung or there is a power outage, the physical PC must be moved to where there’s electricity and a network connection. (I’ve seen this problem more than once.) IT departments also lose the advantages of centralized control, patch management and core app deployment, relying instead on older technologies like SCCM and Windows Server Update Service (WSUS), as well as a third-party tool to update patches on non-Microsoft products. I’ve seen IT departments befuddled when users bring in their MacBooks or other PCs to connect to the desktop that is right in front of them rather than logging directly into their work machine. The reasons vary: comfort of the keyboard as well as running Mac software simultaneously because the VD is just an ICA session. They can also more safely surf the Web and check email without the enterprise snooping on their activity. Many IT departments combine XenDesktop with the older XenApp technology. So once a user authenticates, they have a choice of their personalized desktop or a more generic shared desktop running on Server 2008 or 2012. The advantage of having the two environments running is one serves as a backup to the other. If, for some reason, the desktop broker fails or the PC is off or hung, employees can continue working remotely with the XenApp piece while IT troubleshoots the desktop connection. Citrix supports clients on major platforms: 32-bit and 64-bit editions of Windows 7, Vista SP2 and XP Pro SP3. In addition, there are Citrix Receivers for Mac OS X (Snow Leopard, Leopard and Tiger), Linux, Apple iOS, Google Android and BlackBerry. Those last four are a stretch. Strictly speaking, as an IT admin I wouldn’t use an iOS client to do any administration other than reviewing a console or checking email. Using a finger on an iPad to move a mouse is too ambiguous. Remote computing isn’t new, and it long predates Windows. But Citrix was the first to bring it to Windows and the enterprise. Though it’s the first to the table it’s competing with products from two other companies that have pockets just as deep: VMWare and Microsoft.