Application Virtualization – The Basics

Application Virtualization is the future and it’s more clear today than it has ever been.  I always find it funny how people always revert back to the basics after every other form of architecture is explored.  Application virtualization refers to several techniques that make running applications more protected, more flexible or easier to manage.  Modern operating systems attempt to keep programs isolated from each other. If one program crashes, the remaining programs generally keep running. However, bugs in the operating system or applications can cause the entire system to come to a screeching halt or, at least, impede other operations.  Full application virtualization requires a virtualization layer.  Application virtualization layers replace part of the runtime environment normally provided by the operating system. The layer intercepts all file and Registry operations of virtualized applications and transparently redirects them to a virtualized location, often a single file.  The application never knows that it’s accessing a virtual resource instead of a physical one. Since the application is now working with one file instead of many files and registry entries spread throughout the system, it becomes easy to run the application on a different computer and previously incompatible applications can be run side-by-side.   Examples of this technology for the Windows platform are Cameyo, Ceedo, Evalaze, InstallFree, Citrix XenApp, Novell ZENworks Application VIrtualization, Endeavors Technologies Application Jukebox, Microsoft Application Virtualization, Software Virtualization Solution, VMware ThinApp and InstallAware Virtualization.

Technology categories that fall under Application Virtualization include:

  • Application Streaming-Pieces of the application’s code, data, and settings are delivered when they’re first needed, instead of the entire application being delivered before startup. Running the packaged application may require the installation of a lightweight client application. Packages are usually delivered over a protocol such as HTTP, CIFS or RTSP.
  • Desktop Virtualization/Virtual Desktop Infrastructure (VDI)-The application is hosted in a VM or blade PC that also includes the operating system (OS). These solutions include a management infrastructure for automating the creation of virtual desktops, and providing for access control to target virtual desktop. VDI solutions can usually fill the gaps where application streaming falls short.

Provided below are some basic terms as well as architecutral frameworks when considering in deploying a solution of this nature:

  • Application Streaming=  Rather than installing all applications in every user’s machine, applications are delivered to each user’s PC as needed. This enables the applications to be updated centrally and also provides a way to measure each users’ application requirements over time. See application streaming.
  • Terminals to a Central Computer=  The oldest network architecture, all applications and data are stored in a centralized server or cluster of servers. The user’s PC functions like a terminal to the server or dedicated terminals are used. The applications are said to be “virtualized” because they function as if they were running on the client. See thin client.
  • Partition the Hardware=  This is the traditional meaning of “virtualization” and refers to partitioning a computer in order to run several applications without interference, each in their own “virtual machine.” Deployed in servers and clients, this is more accurately called “server virtualization” and “client virtualization.” Contrast with OS virtualization. See virtual machine.
  • Write the Program Once, Run Everywhere=  An interpreted programming language enables the same program to run on different machine platforms, with Java and Visual Basic being the major examples (see Java Virtual Machine and Visual Basic). The applications are said to be “virtualized” because they run on any platform that has a runtime engine for that language.
  • Dynamic Application Assignment=  This approach treats servers in the datacenter as a pool of operating system resources and assigns those resources to applications based on demand in real time. The pioneer in this area is Data Synapse Inc. The applications are said to be “virtualized” because they can be run in any server.

Benefits of application Virtualization

  • Allows applications to run in environments that do not suit the native application.
  • May protect the operating system and other applications from poorly written or buggy code.
  • Uses fewer resources than a separate virtual machine.
  • Run applications that are not written correctly, for example applications that try to store user data in a read-only system-owned location.
  • Run incompatible applications side-by-side, at the same time and with minimal regression testing against one another.
  • Maintain a standard configuration in the underlying operating system across multiple computers in an organization, regardless of the applications being used, thereby keeping costs down.
  • Implement the security principle of least privilege by removing the requirement for end-users to have Administrator privileges in order to run poorly written applications.
  • Simplified operating system migrations.
  • Accelerated application deployment, through on-demand application streaming.
  • Improved security, by isolating applications from the operating system.
  • Enterprises can easily track license usage. Application usage history can then be used to save on license costs.
  • Fast application provisioning to the desktop based upon user’s roaming profile.
  • Allows applications to be copied to portable media and then imported to client computers without need of installing them.

Limitations of application Virtualization

  • Not all software can be virtualized. Some examples include applications that require a device driver and 16-bit applications that need to run in shared memory space.
  • Some types of software such as anti-virus packages and application that require heavy OS integration.
  • Only file and Registry-level compatibility issues between legacy applications and newer operating systems can be addressed by application virtualization.