Windows NT Server already contains many of the basic components for constructing a clustered system, including:
Single-logon capability inherent in Windows NT Directory Services
Multisystem monitoring capability of administration tools and the Windows NT Performance Monitor
The ability to route requests via the redirector
Windows NT Server cluster enhancements represent a spectrum of technologies that will continue to be phased into the Windows NT Server and BackOffice products over time. Microsoft has prioritized additional clustering features based on customer requirements.