Virtualization is one of the hottest buzzwords in the IT industry today, yet many people are not sure just what it is. Currently, virtualization refers to a group of technologies that can improve efficiency and lower costs for delivering IT infrastructure services. Leading vendors that provide virtualization software include VMware, Citrix, and Microsoft.
The most common type of virtualization is server virtualization, or the process of subdividing a single computer into multiple partitions (also known as virtual machines). Market-leading products for server virtualization include: VMware ESX, Citrix XenServer, and Microsoft Hyper-V. This process has existed on large-scale mainframe systems for over 40 years, but has found its way into standard PC hardware in the last few years. Each virtual machine is isolated from the others running on the same computer. To the software (operating systems and applications) running in these partitions, each virtual machine appears to be a complete computer system.
While this partitioning process consumes some computing power, it has many benefits. Many computers are underutilized; multiple computers may be consolidated into virtual machines running on a newer, higher-performing, and more energy-efficient computer. It is also much less time-consuming to maintain software running in virtual machines. Some server virtualization software can move a virtual machine from one physical server to another without causing an outage! This allows companies to more flexibly manage how their computing power is allocated – at different times of the day, and across various departments.
Similar benefits can be applied to desktop workstations through desktop virtualization or virtual desktop infrastructure (VDI). Leading products for desktop virtualization include VMware View and Citrix XenDesktop. This type of virtualization consolidates all the desktop PCs in an office onto a small number of servers running in a data center. With staff desktops running in a centralized and controlled environment, desktop virtualization can greatly reduce support costs associated with maintaining desktop and laptop PCs. Virtual desktop infrastructure also helps organizations secure sensitive data, by maintaining it in a centralized data center, or encrypting the desktop environment, so a lost or stolen laptop will not lead to a security breach. This is the most flexible solution for delivering the end-user desktop experience, but is more costly than a “thin-client” or “terminal-based” solution.
A third type of virtualization is application virtualization. This is a new name for existing “thin-client” or “terminal-based” computing solutions, such as Citrix XenApp (MetaFrame) or Microsoft Terminal Services. With application virtualization, all processing is done on shared servers in a data center. Users’ desktops and laptops either can be replaced with inexpensive terminal devices, or run software to act as “dumb terminals” – merely a display, keyboard, and mouse. Application virtualization greatly simplifies the configuration at users’ workstations, allowing maintenance to be concentrated in the data center. It is most beneficial for “task-based” users who work in a single location. “Knowledge workers” and mobile users are often better off with a desktop virtualization solution, as it gives them a dedicated virtual desktop to run a customized mix of applications.