IIS 5.0 Isolation Mode (IIS 6.0)
IIS 5.0 isolation mode provides as much compatibility as possible for applications that were developed for IIS 5.0. For example, the request processing of IIS 6.0 when it is running in IIS 5.0 isolation mode is nearly identical to the request processing of IIS 5.0. Hence, in IIS 5.0 isolation mode, you can run read raw data filters and can run applications in Inetinfo.exe or in DLLHost.exe — all of which is not accommodated in worker process isolation mode.
Before you decide to run an application in IIS 5.0 isolation mode, carefully evaluate whether you can substitute other filters and applications for the ones that require IIS 5.0 architecture because when a server is running in IIS 5.0 isolation mode, application pools, recycling, and health monitoring features are unavailable.
For more information about evaluating application isolation modes, see Evaluating Application Isolation Modes.