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Microsoft® Windows Server™ 2003 White Paper

Scalability features such as out-of-process session state management allow applications to be deployed across a Web farm for greater throughput and reliability.

Processes are generally started on-demand, i.e., only when they are needed, so as not to consume resources unnecessarily. They can also be killed after a specified idle time. This allows a single server to serve more applications than was practical in prior implementations. Set the idle timeout to shut down a process if it is idle for given period of time and free up resources for active applications. Consider disabling idle timeout if application startup takes a long time.

Applications can be swapped and restarted on the fly, and a Web site can be restarted without affecting other Web sites on the same server. Eliminating down-time boosts effective performance as users are never waiting for a response from a crashed server. Furthermore, fewer extra servers are needed to handle the load during maintenance.

Running safe out-of-process processes doesn’t require additional context switches from the IIS process to the application process as it did before.

Optimizations were made to global PFN lock acquisition on both 32-bit and 64-bit systems.

Improvements were made to dispatcher lock acquisition during context switching. The dispatcher lock assures synchronization between different threads and different CPUs. It is acquired whenever you need to scale a thread or perform a synchronization operation like setting an event, acquiring a mutex, setting a semaphore, or using any of the .NET synchronization objects. On systems with a large number of threads and processes, performance will improve between 15 and 20 percent.

Windows Server 2003, Enterprise Edition, and Windows Server 2003, Datacenter Edition, both support Hot Add Memory. This allows ranges of memory to be added to a computer and made available to the operating system and applications as part of the normal memory pool while the server is running. This does not require re-booting the computer and involves no downtime. This feature will be available only on hardware that supports this feature.

Scalability Case Study

The NILE application was tested for scalability using an e-commerce benchmark from Doculabs, which measures the overall performance of some scenarios that are commonly used by e-commerce sites, including logon, browse items, search, shopping cart operations, check out, static file caching, data-base operations, and session state management. Results showed that ASP.NET ran more than twice as fast than ASP whether running on Windows 2000 or Windows Server 2003. The best performance was obtained using ASP.NET on Windows Server 2003, which ran more than three times as fast as ASP on Windows 2000. The application scaled up well too—performance with four and eight processors was approximately 250 percent and 350 percent faster, respectively, than benchmarks with one processor. The following figure shows a graph of the performance results.

Implementing a Scalable Architecture7

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