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While it is important to understand the way Thin Clients bring the benefits of mainframe computing to PC based applications, it is also important to understand the parts that are required to get the system up and going. There are actually several pieces from different vendors that are required to make a Thin Client system. The four most important are the Server, the Server Operating System, the client management software and the Thin Clients themselves. Although sometimes purchased from a single supplier, they all come from different vendors originally.
Just like in a mainframe installation where the mainframe itself is the most expensive and complex part, the single most expensive item in a Thin Client installation is the server. The server will host every application that is controlled from any of the connected Thin Clients. The clients themselves have passed their ability to actually run programs up to the server, and consequently the server must have the capacity to handle all of these tasks. Replicating the functionality of 25 or more PCs requires the server to have extra CPU cycles and extra memory. Disk space is not really a concern - as clients share applications they can share disk space as well. An application that must be run on any (or all) of the clients only needs to be installed one time, and so takes up no more space on the server's disk drive than it would have taken up if installed on a local machine.
The server's CPU is now doing the computing for each and every task that would have been handled by the clients - if Microsoft Excel will be running on every connected client, the server will have to be able to service the needs of multiple instances of the application. This, however, is not as hard as it originally seems. If a test is done of the CPU utilization of a standard desktop computer during normal operations it is found that rarely does the processor load go above 3 or 4 percent. This is because the ability of available hardware is far above what is required to run current programs. Even when the processor load does climb, it is only for short periods. What this means is that while a server that will host 25 clients needs to have a capable processor(s), it does not need to have a processor that is 25 times as powerful as would be required if distributed machines were used instead. As an example, a server that is taking the place of twenty five 450Mhz machines could probably get by easily with two 700Mhz CPUs.
Memory usage, however, is linear. Each application started from one of the clients will be running on the server and will need its own memory space. Consider an application that requires 125 MB of memory to operate comfortably. 25 instances of this same application running at the same time on the server will use up roughly 25 times the memory on the server.
Fortunately, setting up a Thin Client system became much easier with the release of Microsoft Windows 2000 Server. Support for terminal services, once a part of a special version of NT, have now been rolled into all of the standard versions of Windows 2000 Server, and can be enabled at any time. When Microsoft added the ability to connect Thin Clients to every server OS that they sold, they also started enforcing connection licenses. So to run 25 Thin Clients on a standard Windows 2000 Server, you must purchase 25 Terminal Services Client Access Licenses (TS CALs) from Microsoft in addition to the standard Client Access Licenses (CALs). TA CALs are per seat (client) while the standard CALS are concurrent. Currently there are three levels of Windows 2000 Server: Standard, Professional and Advanced. For the highest level (Advanced) Microsoft throws in 25 CALs for free.
Because Thin Clients are based on a centralized computing model, all of the clients are run from one or more Windows servers. These servers host all of the client's applications, and so they are also the perfect place to handle all of the System Administration responsibilities. In fact, without a good server side management software package, it is next to impossible to get even a few thin clients online.
The user needs to be able to easily create a new terminal, or replace a damaged terminal. Clients stationed at different locations will frequently have different functions, which may require that they have different configurations. Administrators should be able to use the management software to set the IP address of the hosting server(s), the Windows Username and Password (if unprompted logons are desired), and the video resolution and monitor characteristics for each client. And for an industrial application, configuration of a client's touchscreen and identification of failover servers are essential.
If any properties of a terminal have been changed, the System Administrator should then be able to restart any of the affected terminals from the management interface. As the client's software is running on the server, this will not affect the operation of any applications that are being displayed on the client.
The final piece in the Thin Client system is the client hardware itself. Thin Client hardware is not complex (the very word 'thin' comes from the fact that it has been stripped of all unnecessary parts) and should be the easiest part of the system to install. For a system that is using ACP's ThinManager as the management software, configuration of a new Thin Client generally involves little more than plugging it into the Ethernet network and turning it on. Any client purchased from a company that sells ACP Enabled Thin Clients will then seek out the management software and bring itself online.
What this all means is that a Thin Client system can be set up as follows:
Once configured (either manually or automatically) each client will then boot and display the Windows 2000 session screen that has been defined for that particular user. Any application that needs to be operated from the clients must now be installed on the server (but only once) and every authorized client will have access.
For more information on ACP Industrial Thin Client computers, please visit our web site at http://www.thinmanager.com
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