[This is preliminary documentation and subject to change]

# Scalability

Scalability is a characteristic used to describe whether or not a piece of hardware or software easily expands to meet future computing needs. Internet Information Services (IIS) is designed to scale, however scalability can be impaired by hardware configurations. Administrators can dramatically improve the scalability of their IIS server environment with careful planning and assessment of their infrastructure, which includes hardware, distributed applications, and custom components. The topics in this section describe how to assess and plan for improved scalability with your IIS Web server.

Note Consider enabling Dedicated Application Mode. Dedicated Application Mode forces applications to run in an isolated environment. Isolating applications in this way reduces bottlenecks and points of contention, which typically improves scalability and performance.

This section includes the following topics:

- About Scalability: This topic describes scalability, methods for scaling, and how to plan and design scalability into a Web server environment.
- Scalability Testing: This topic describes scalability testing and tools for scalability testing.
- Scaling Up: This topic describes the possible gains and regressions administrators might experience when trying to improve scalability by adding resources like RAM and CPUs to a server.
- Scaling Out: This topic describes the possible gains and regressions administrators might experience when trying to improve scalability by adding more Web servers to their existing system. This topic also describes Web farms and Web gardens.
- Scaling Down: This topic describes the benefits of converting real sites to virtual sites and how, by assessing idle capacity in your server environment, you can improve scalability.
- Host Scaling (Administering Large Quantities of Sites): This topic describes how to store thousands of sites on an IIS server and how to efficiently administer those sites.

Microsoft.com offers scalability scenarios and solutions using other Microsoft products like Application Center, BizTalk Server, Commerce Server, and Sequel Server. Visit www.microsoft.com/servers for more information.

This section does not include information on:

- Performance effects of site content choices; see Configuring Applications and Developing Scalable Components.
- Connection Performance; see Network Capacity.
- Developing Scalable Web Applications
- Developing Scalable ASP Applications
- Developing Scalable Components
- Data Access Performance

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