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Determining the number of Thin Clients required for an installation is easy - finding the right size server is more difficult. This article discusses general server sizing guidelines, and then gives some specific recommendations.
While the first thing that most people think about is the processor speed, our experience shows that the amount of RAM available in the server actually has more of an impact. Dual CPUs are always helpful, but many industrial applications can only use one of the CPUs. The second processor is still helpful, however, because the system programs will start to move over to it as the first processor (Processor '0') becomes more utilized.
Right before Microsoft released Windows 2000 Server, ACP did extensive testing with it to discover the resource requirements of typical industrial Thin Client systems. After all, users would now be moving all of the processing that was taking place on many distributed machines to a single machine, so it made sense that the resources used by those machines should be moved from the Thin Clients (where they were no longer needed) onto the server. That is easy to do with RAM and disk storage, but what about processor speed?
It turns out that on most distributed PCs the RAM is completely utilized all the time, while the CPU spends much of its time in an idle state. ACP ran tests with the most common HMI packages. Looking at a number of different factors, we came up with recommended servers required to run industrial software applications. While you may no longer be able to buy similar machines, many customers are still running servers with very acceptable performance based on the following guidelines:
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5 Thin Client system
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15 Thin Client System
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25 Thin Client System
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Pentium III 450 MHz
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Pentium III 500 MHz
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Pentium III 700 MHz
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384 MB RAM
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384 MB RAM
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384 MB RAM
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There is no reason, especially for small systems, why the Terminal Server cannot serve all of the Thin Clients and do other things as well. It is very common for a 5 or 10 client system to have only a single Terminal Server that provides the user interface for all of the clients, runs a data collection database and requests I/O. Once the system gets beyond about 10 clients (with industrial software applications) it just makes sense to split the processing among several machines.
A better way to run a system with 10 or more clients is to break it up into two primary servers. In that case, the machines don't need to be top of the line, and prices for the smaller machines have fallen off considerably. If you need 10 clients, seriously consider getting two machines that would both max out at 10 clients and put only 5 clients on each one. If it would run OK with 10, it will fly with 5. Use ACP failover to have each of the clients fail over to the other machine if its own server has a problem, and you have a very nice system.
Once the number of industrial clients on a single machine gets over 25, it is really a good idea to split the processing among multiple servers. No matter the size of the server, ACP currently recommends that no more than about 30 industrial applications be run on a single machine. Although we sell severs that will run 50 sessions concurrently, these should be used more to support the 50 sessions during the failure of a server and not as standard operating procedure.
A very important factor in picking the correct server is the application. If you have been to some of our training classes, you have seen us run as many as 10 Thin Clients (and sometimes more) from a single laptop computer. That is because we are running small programs like our ThinManager user interface, notepad, Excel, etc. For applications similar to those a summary of testing done by Microsoft shows the following server requirements:
For what they term "Data Entry Workers":
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320 Client System
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280 Client System
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2 Pentium III 450 MHz
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1 Pentium III 450 MHz
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1024 MB RAM
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1024 MB RAM
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If the user is going to be switching between multiple applications (what they call a "Knowledge Worker") the number of users on the same machines drops considerably:
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160 Client System
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70 Client System
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35 Client System
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8 Pentium III 500 MHz
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2 Pentium III 450 MHz
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1 Pentium III 450 MHz
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4096 MB RAM
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1024 MB RAM
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1024 MB RAM
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Note on RAM requirements - Microsoft estimates that a Knowledge Worker will require 9.3 MB per client, and a Data Entry Worker will only require 3.5 MB per client.
ACP currently sells a full line of Advantech servers, configured with all of the Microsoft and ACP licenses needed for a "plug and play" system. These servers are sized for the most demanding industrial applications, and as you can imagine actually have resources to spare. Here are our current suggested server configurations:
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5 Client System
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15 Client System
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20 Client System
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25 Client System
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50 Client System
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1 GHz PIII CPU
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1.26 GHz PIII CPU
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2 1 GHz PIII CPUs
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2 1.26 GHz PIII CPUs
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2 1.26 GHz PIII CPUs
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512 MB RAM
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512 MB RAM
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1 GB RAM
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2 GB RAM
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3 GB RAM
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For more information on ACP Industrial Thin Client computers, please visit our web site at http://www.thinmanager.com
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