Server virtualization gets most of the glory, but it's application virtualization that may ultimately have a more significant impact on enterprise IT architectures, supporting new modes of business and smoothing the path to the new services-oriented online structure known as the cloud. \nApplication virtualization has been around a while, and many IT shops use it in one form or another. In the form of terminal services, application virtualization is employed in most large organizations to support remote offices. At the individual application level, virtualization is used to obviate compatibility issues when installing new apps across a wide network of users. \nLately, the ongoing migration to Windows 7 has spurred the use of application virtualization tools to ensure that older but still critical applications run on the new OS. \nApplication virtualization is also being used to prep a push into virtual desktop infrastructure (VDI). And despite initial skepticism, virtualization is moving to the most critical applications\u2014those that organizations depend on to run their businesses\u2014such as ERP and database. Agility and FlexibilityVirtualization, in general, refers to isolating or unbinding computing resources so that they can run without depending on a particular platform or environment. Virtualization applies to both hardware and software, and can be used in connection with servers, storage and applications. \nApplication virtualization itself can have multiple meanings. That's why some experts say application virtualization is better addressed according to the problem you're trying to solve. "It's a business conversation more than just a technology conversation," says Kevin Strohmeyer, senior product manager for the enterprise, desktops and applications group at Citrix, which markets both terminal services and application virtualization technology. \nApplication virtualization offers business advantages in terms of agility and flexibility. For instance, app virtualization can be a cost-effective strategy when setting up a temporary office or a limited-run project. Because of virtualization's ability to contain and control messy interactions with the operating system, a virtualized application will leave behind very little digital detritus. That allows a server purchased for one project to be re-deployed much more quickly and efficiently when that project is completed. Forced MarchThe biggest impetus these days for employing application virtualization is the forced march to Windows 7. Even organizations that sat out the upgrade to Windows Vista are moving to Windows 7, and as might be expected, they occasionally run into application conflicts. \nTax software giant Intuit, for example, needs to keep running older versions of its tax software to support customers still operating on those older versions and calling in looking for help, says Michael Caouette, senior engineer with the company's employee services IT Group. Then came Windows 7. "We ended up with a lot of application compatibility problems," he says. \nHis group uses Microsoft's application virtualization technology, App-V, as well as that from a third-party vendor, InstallFree. He says they've virtualized as many as 30 apps so far, including IE6-based apps, Adobe Acrobat Reader, Firefox and Quickbooks. \nVirtualization helps with application compatibility and aids in the installation process because "I only have to stream [the virtualized application] down to the desktop," Caouette says. \nSimilarly, Autodesk, the CAD\/CAM software developer, needed to support the client side of its Seibel sales force system, which uses the IE 6 browser as its interface, when the IT organization shot-gunned 12,000 nodes of Windows 7 throughout the company. Scott Baker, application programmer\/analyst in the desktop support group, says Microsoft's app virtualization technology was no help because "App-V did not support the virtualization of IE6 ." So Baker used InstallFree to keep the legacy-yet-critical Siebel call center application up and running. Overcoming LimitationsThere are scenarios that do not lend themselves to application virtualization. For instance, it can be difficult\u2014if not impossible7mdash;to virtualize applications that interact in a significant way with the operating system at the kernel level. From a less technical standpoint, if an organization standardizes enterprise-wide on a specific version of an application or application suite, it probably makes sense to run that software natively. \nOne of the limiting scenarios, however, used to involve virtualizing "mission-critical" server-based applications. Conventional wisdom had it that there were too many architectural challenges, too many potential "gotchas," such as IP hooks and security issues, to make virtualizing server applications feasible. But that's changing. Microsoft is now testing a version of its application virtualization technology for Windows server applications, known as Server App-V. And at least one third-party vendor, AppZero, is touting its virtualization technology for server apps that run on a variety of OS platforms. \nServer App-V will be part of a new version of Microsoft's System Center management console, and is intended to be used with Microsoft's cloud software and service, Azure. AppZero's virtualization technology allows applications to migrate to various server platforms, such as moving legacy applications to updated environments. \nGreg O'Connor, CEO and president of AppZero, says he has two types of customers: ISVs looking to ship server applications for the Windows platform without the help of Microsoft; and end-users looking to migrate critical server-based applications to managed services providers and the cloud. \n"We can make it so you can pick up an Oracle database and move it from your data center to the Amazon storage cloud and then to RackSpace," O'Connor says. \nThe opposite is also true, O'Connor points out. Virtualized server apps can be moved back into an organization's data center with relative ease, mitigating the risk of "vendor lock-in" to a specific cloud services provider. The Mobile ImperativeThe virtual desktop is not the same thing as the virtualized application\u2014but they complement each other. The virtual desktop is an "image" of what the user wants and\/or needs on a PC, laptop or thin client (OS, apps, user profile, etc.), streaming over the network from a remote server. Because app virtualization ensures application compatibility and flexibility, it supports a stable yet easily updateable "single image" virtual desktop environment. \nNSK Corp., a global auto parts dealer, employed InstallFree's application virtualization technology to support its IE6-based applications when it began its move to Windows 7, says Todd Warner, LAN\/WAN supervisor. Now he's using it to make PC support easier across the organization. Users can install their applications automatically from a self-service portal, which "cuts down on desk tickets," he says. \nWarner is considering application virtualization in connection with VDI. NSK is "starting to virtualize desktops for developers," he says, using VMware's virtual desktop technology, VMware View. By virtualizing applications for developers, those virtual desktops can be updated "automatically," across the organization, Warner says. \nHe's also "playing with [application virtualization] for tablets\u2014Galaxy, iPad 2 and Zoom," Warner says. "We have a lot of executives wanting to use iPad 2s." \nApplication virtualization aimed at mobile devices is the next step. Not only does virtualization make mobile apps easier to migrate across servers and easier to support in a virtual environment, vendors are starting to offer tools to develop virtual apps that run on smartphones and other mobile devices. For example, VMware markets its Mobile Virtualization Platform, which is designed to enable developers to build mobile apps for multiple environments and to let users have multiple profiles on a single device. A Virtual WorldVirtualization has been, and continues to be, one of the building blocks of the Web 2.0 corporate infrastructure. For IT managers, hardware virtualization is having a direct impact in terms of ROI dollars right now. The ramifications of application virtualization are less direct, longer term, but potentially more significant and meaningful in a highly mobile world. As NSK's Wartner says, "Once I have it virtualized I can push it anywhere I want." \nIn light of the onslaught of virtualization, and in particular the potential of application virtualization, the marching orders for IT managers are obvious, says Alon Yaffe, director of marketing at InstallFree: "IT needs to start managing more things on the back end and less things on the client."