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What is a Terminal Server?
A terminal server is a server or device that connects terminals such as PC's, printers, and other devices to a local or wide area network. Other devices connect to one side of the terminal server through their RS-423 or RS-232C serial port. The other side of the terminal server then connects to a Local Area Network (LAN) or Wide Area Network (WAN) through the network interface cards (NIC).
Because the connection resources inside the terminal server are usually shared dynamically by all attached terminals, this means that each attached terminal does not need its own network interface card or modem. In a Terminal Server environment, the application processing and data manipulation or execution occur on the server.
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What is a Virtual Desktop?
When the term "virtual" is used in computing it means roughly that the device is "not real." There is a virtual computer, or virtual machine. However, the real operation or the interface originates somewhere else. This is the virtual desktop infrastructure (VDI).
The client/server model is the basis for the VDI. It is also referred to as server-based computing (SBC). In a VDI environment, a virtual machine means that you would have a "computer" inside a computer. The virtual machine, the client, acts like a real computer. However, it is under the control of the computer that is running the virtual software, the server.
So in that context, a virtual desktop is a user's interface in a virtual environment. The virtualized desktop is located on the real, physical local machine. In a virtual desktop the user can interact with the virtual computer just like he would with a regular computer. Programs can be run. Reports can be printed, and even Internet browsing can be accomplished.
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Working With Terminal Servers and a Virtual Desktop
Virtual desktops can be used by management. One of the more powerful features is that you can put multiple virtual machines on one computer and run them simultaneously. For example, assuming that the host computer is sufficiently powerful, with say 8 gigs of RAM and a quad core processor running between 2.3 and 2.9 gigahertz, you can run three virtual machines on the system. One of the VM's could be a database server, another a finance server, still another a sales server. Running these three servers on a real box saves money and management time. The same operations that would be done on a real machine, can be accomplished in the virtual machine.
This can change the use of the terminal server. While a terminal server can connect multiple clients to itself, the terminal server is typically performing one operation. With the virtual machine environment, client computers can connect to the virtual machines, so that the local physical machine that supports the virtual machine can become a terminal server, in a virtual machine environment.
Thus the best performance operations of both worlds can be accomplished by the VDI.
This image shows how you can put two virtual machines operating on one physical computer. This is the "computer" in a computer.
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Terminal Servers allow clients to connect in order to perform data operations on the server, but the results are viewed or seen on the client. Virtual desktops are part of a virtual machine and sit on a real computer. You can put several virtual machines on a server, each acting independently of the others but ultimately under the control of a real computer station. Several clients can then access the virtual desktops and perform operations themselves as if they were on a terminal server system.