This behavior was what gave Microsoft's operating systems a bad reputation in the first place. ![]() If an error occurs, the best way to solve the problem is not by rebooting the server. We recommend keeping the default setting, and only letting applications with the highest priority run as isolated processes. All other applications will be run in a single, pooled process using dllhost.exe, unless you manually change the settings. The default setting for application protection specifies that Web services in inetinfo.exe will run in their own processes. You can select High (Isolated), Low (IIS Process), or Medium (Pooled) from the Application Protection drop-down list.įigure 7-4: Setting the application protection for a Web application or site You can only set this on the Home Directory or Virtual Directory properties sheet of a Web site. Microsoft has tried to overcome this performance drop by looking over the IIS 5.0 code, but our recommendation is not to run more than ten isolated applications on a server.įigure 7-4 shows how to set the application protection level for a specific site. In this case, performance is negatively affected by running pooled or isolated applications. This application will then be run in a separate instance of dllhost.exe, making it hard for other applications to bring it down with them if they encounter an error.īut all good things usually come with a price tag. If you have a very important application, you can run it as an isolated process. All applications in the pool will fail, but the Web server will still be up and running. If you run applications in a pooled process, an error will not take the whole server down. This solution is called application protection and provides for a much more stable and reliable application architecture than was possible before. This is also an out-of-process procedure handled by the dllhost.exe.įigure 7-3: The three different ways an application can be run in IIS 5.0 Running applications in a pooled process separate from Web services. Running applications isolated from Web services in a process called dllhost.exe, which is called out-of-process. Running applications in-process in the Inetinfo process. IIS 5.0 provides three ways to run your applications, as listed here (and illustrated in Figure 7-3): Performance for one thing was high, but honestly the disadvantages were so great that this was not enough to promote this technology in the long run. You might think such an approach to running applications had too many drawbacks, but it had its benefits, too. ![]() This provided some problems naturally, since all Web sites hosted on the server became affected by this. Another problem with such applications was that they could not be unloaded without a restart of the entire physical server. When an application is run like this, it is said to run in-process. One of the problems of versions of IIS prior to version 5.0 was that a single application error could bring down the entire server, due to all Internet Server API (ISAPI) applications (like ASP) sharing the resources and memory of the Inetinfo process. But as you will see, there is a limit to how much RAM IIS can handle, which you also have to consider. The remedy is to provide enough RAM to your Web servers so you can avoid paging and keep the Inetinfo process in RAM at all times. This means the system can remove all or part of this process from RAM and write it to disk if not enough RAM is left, which negatively affects IIS performance. This process also contains the shared thread pool, cache, and logging services of IIS. The Internet services in IIS 5.0 reside in the Inetinfo process (inetinfo.exe). Figure 7-2: An overview of the IIS 5.0 architectureĪll Windows-based services and applications are run in memory areas called processes.
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