Product Reviews

How Much is Too Much?

WCAT can answer that question.

I remember an advertisement for a start-up dot-com which showed them launching their Web site for the first time. The team all gathered around and watched as the hits started to role in. The problem was the hits kept coming faster and faster and faster. The dot-com was unprepared for what their Web servers could handle. Do you know what your Web servers can handle? Do you know how much is too much? The Web Capacity Analysis Tool (WCAT) from Microsoft can help you figure that out before you get a nasty surprise.

WCAT is one of nearly 300 tools available in the Microsoft Windows 2000 Server Resource Kit. WCAT runs simulated workloads using client-server configurations. Using WCAT, you can test how your Internet Information Services (IIS) and network configuration respond to a variety of different client requests for content, data, or HTML pages. You can test different server and network configurations by using the prepared WCAT content and workload simulations. You can use WCAT to test servers with single or multiple processors and to test servers that are connected to multiple networks. WCAT will test response time for SSL and PCT encrypted connections and well as test response time for scripts such as Active Server Pages (ASP).

WCAT is made up of three components: the WCAT Server, which is the system being tested, the WCAT Controller, which administers and tracks the test, and the WCAT client, which tests the server. This design allows for the system being tested to only be loaded by Web requests, without the burden of processing test administration as well. The WCAT client application runs in a single, multithreaded process that can spawn multiple threads, each representing a virtual client that then throws page request at the server. WCAT can support up to 200 virtual clients on each client computer involved in a WCAT test, and the WCAT Controller can coordinate multiple client computers.

WCAT includes many predefined tests for basic operations, including HTML and ASP requests, "keep alive," and SSL operations. These predefined tests allow you to get up and running quickly with your analysis. In addition to the predefined tests you can create your own tests and use Performance Monitor Counters to enhance the data that you're gathering from your system.

WCAT is a command line based program so it takes very little space on your system and can be easily run periodically to set benchmarks and compare results as configurations change. Once WCAT is installed and configured the command line interface makes it easy to script and schedule the tests to run automatically.

WCAT is an inexpensive way to test different configurations to see which one will be the optimal configuration for your applications. If you're expecting a substantial load on your IIS server, running these tests before you deploy will help ensure that the hardware is up to the task.

About the Author

Stewart Cawthray, MCSE, ITIL Service Manager, is an IT management consultant for Hewlett-Packard.


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