Server Roles

In a client-server networking environment, there are client workstations and servers which perform special tasks. The types of roles a server can fill under Windows NT Server 3.5/3.51 are described in this section, which begins with the minimum requirements for a Windows NT Server domain.

Primary Domain Controller

The minimum requirement for a domain is one server running Windows NT Server 3.5/3.51, which acts as the Primary Domain Controller (PDC), and stores the master copy of the domain's user and group security accounts database (SAM).

A domain has only one PDC.

Backup Domain Controller

A domain may have any number of Backup Domain Controllers (BDCs) running Windows NT Server. While not required, one or more backup domain controllers in a domain provide load balancing and fault tolerance. A BDC contains a copy of the domain's or master domain's SAM and can be used to authenticate user logons to help spread the load of logon request processing. The SAM is replicated to all the Backup Domain Controllers in the domain. If the PDC goes down, a BDC may be promoted to the PDC. The administrator should consider having as many Backup Domain Controllers as needed to process a high volume of logon activity at the desired performance levels. Each BDC can support up to 2000 user accounts.

Servers (non-domain controllers)

Servers dedicated for other uses can also run Windows NT Server software, but function as neither a primary nor backup domain controller. These servers can be standalone workstations, may participate in a domain as a file or application server, or may house BackOffice components. These servers do not participate in the replication of the user and group database, or the logon authentication process.

Some reasons for implementing non-domain servers are:

• • The server must perform business-critical tasks or services, and should not spend any resources authorizing user logon requests or replicating the user database.
• • The administrator for this type of server might not be allowed administrator rights for the rest of the domain.
• • The server might be moved to another domain in the future.
• • A non-domain server can be used to administer the domain server.

Just like a Windows NT Workstation version 3.5/3.51, the server will have its own security accounts database which it will use for User level security. Like the workstation, the server will be able to join a domain and use the domain's SAM to assign permissions to its own shared resources. If the network does not have a domain, the Windows NT Server can create or become a member of a workgroup just like Windows NT Workstations or Windows for Workgroups systems.