This article is excerpted from Practical Virtualization Solutions: Virtualization from the Trenches and published by permission of Prentice Hall, all rights reserved.
Desktop virtualization, briefly, is moving a traditional desktop operating system from local hardware to a remote server system. The remote desktop is accessed by utilizing some lightweight client in the form of a small or minimal operating system (smart terminal) or a dumb terminal that has only enough programming to inform it of the whereabouts of the desktop.
Desktop virtualization is attractive to enterprises because it promises to minimize costs associated with managing hundreds or thousands of desktop computers, operating systems, patches, software, and user support issues. The unfortunate truth is that, depending on the way desktop virtualization is implemented, the cost savings may disappoint all but the most pessimistic onlooker.
This chapter examines several methods of desktop virtualization and describes how each is implemented. The pros and cons of each solution are discussed so that when the time comes to put a project plan together, you can make an informed decision and have a smoother transition to virtualized desktops.
Terminal services, the oldest type of desktop virtualization, still may be the best all-around solution available for most applications. The speed, centralized management, lack of specialized or extensive user training, and overall user satisfaction may be hard to beat by other forms of desktop virtualization.
You may recognize the term 'terminal services' from Windows Terminal Server or Windows Terminal Services, but the concept and the practice predates Windows by a decade or more. Terminal servers are server systems with terminal services enabled. The terminal server may be UNIX, Linux, or Windows. The desktop experience you receive depends on the terminal server's operating system. You can't get a Linux desktop from a Windows Terminal Server, nor can you get a Windows desktop from a UNIX or Linux Terminal Server.
[See also Hosting virtual desktops: Tips for a successful outcome. And for much more information, check out Complete coverage: Desktop virtualization.]
After you connect to a terminal server, your user experience depends largely on the administrator who set it up and any corporate standards that may be enforced. For a Windows Terminal Server, you'll see a standard Windows desktop with the familiar look and feel of a standard Windows desktop operating system. The behavior of the desktop, applications, and printing are the same as if you were using a local computer. More often than not, users report that the terminal server is far faster than their old desktop computer, and they are quite pleased with the perceived upgrade. ...
A smart terminal is a minimal computer equipped with a minimal operating systemperhaps even an embedded one. A smart terminal has limited processing power because its entire job is to connect you to a remote server system. The operating system is graphical and has a small number of icons or hyperlinks that you can use to connect to different resources.
Smart terminals connect to Terminal Servers by some protocolCitrix ICA, RDP, VNC, XDMCP, and the like. Users, after authentication, are presented with a desktop and all the applications they would see if they had logged on locally to the remote system. Remote terminal services are very fast and efficient for the end user. Modern Terminal Servers can even redirect sound to the users terminal for an almost local desktop experience. Video quality is also very high24-bit color is standard.
Prices for such hardware are falling while functionality is ever increasing. You can purchase smart terminals for about the same price as a low-end desktop computer. The terminal has fewer moving parts and has a longer life expectancy than a standard desktop computer.
Classic dumb terminals are almost nonexistent these days. Thin clients have taken their place as the next-generation dumb terminals. These devices have a small set of utilities embedded in them so that they can be configured locally, remotely, via a web browser, or some other proprietary provisioning software.
After the terminal is provisioned or configured, the user is automatically directed to the appropriate server when the unit is powered on. These devices are generally single-homed (configured for a single Terminal Server), unlike the smart terminals that can connect to a user-selectable array of available resources.
Dumb terminals are very cost effective, typically priced in the $200 USD neighborhood. Minimal cost, minimal configuration, and practically no maintenance make this an excellent choice for a desktop virtualization solution. The major drawback to a dumb terminal is that it is single-homed.
Terminal services receive high praise for speed, productivity, and ease of administration. Consider this desktop virtualization solution near perfect for all bandwidth situations from dial-up to Gigabit Ethernet LANs.