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isolation mode and others in IIS 5.0 isolation mode. If applications require separate modes, the
applications must run on separate servers.
Compatibility Issues
After you perform an upgrade of the operating system, IIS is configured to run in IIS 5.0 isolation
mode by default. Before configuring IIS 6.0 to run in worker process isolation mode, you should
evaluate whether your Web sites and applications are compatible with worker process isolation
mode. Most of the compatibility issues with IIS 6.0 occur when configuring IIS 6.0 to run in worker
process isolation mode.
One of the most common reasons for incompatibility with worker process isolation mode is that
applications do not recognize custom ISAPI extensions or DLLs that depend on the memory and
request processing models used by earlier versions of IIS. Determine application compatibility in
your lab before upgrading your existing IIS server, and if you determine that your applications are
not compatible with worker process isolation mode, you can run the applications in IIS 5.0
isolation mode.
Isolation Mode Matrix
Upgrade Path/Needs
IIS 5.0 Isolation
Mode
Windows NT 4.0: Upgrade to Windows Server 2003
D
4
Windows 2000: Upgrade to Windows Server 2003
D
5
Application with dependency on older memory model:
Needs to run in-process with IIS or has dependency on
System account
D
ASP.NET 1.0: Previously installed and dependent on
1.0 behavior not .NET Framework 1.1
D
Process
Isolation Mode
D
Windows NT 4.0: Clean install of Windows Server 2003
Need for most secure model, application recycling
abilities, and new features of IIS 6.0
D
Enabling IIS 6.0 After an Upgrade
For security reasons, the WWW Publishing service is disabled when you upgrade from Windows
2000 Server or Windows 2000 Advanced Server to Windows Server 2003 or Windows
Server 2003, Enterprise Edition, respectively. In a Windows 2000 Server installation, IIS 5.0 is
installed by default, and in many cases the WWW service was not used. As a result, the WWW
service is now disabled after an upgrade.
4
IIS is not disabled by upgrade.
5
IIS is disabled by default
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