Choosing a domain model

Nodes in a server cluster can be either member servers or domain controllers. However, in either case, all nodes must belong to the same domain.

If you configure your cluster nodes as domain controllers, you must first make sure you have the hardware to support them. For more information, see Capacity planning.

If you configure all of the cluster nodes as member servers, then the availability of the cluster will depend on the availability of the domain controller. The Cluster service requires that the nodes be able to contact the domain controller to function correctly, so the domain controller must be highly available. To avoid a single point of failure, the domain must have at least two domain controllers. For more information on increasing availability, see Addressing risks using server clusters.

At least two domain controllers must be configured to be global catalog servers.

DNS considerations

If DNS is used to resolve names in the domain, then you must deploy at least two Domain Name System (DNS) servers. If your cluster nodes are the only domain controllers in their domain, they must be configured as Domain Name System (DNS) servers. Make sure that the DNS servers support dynamic updates. For more information on DNS, see DNS.

Each domain controller and cluster node must be configured with a primary and at least one secondary DNS server. If the domain controllers are also DNS Servers, then make sure each points to itself for primary DNS resolution and to the other DNS servers for secondary resolution.

Performance considerations

Take into account the additional overhead that is incurred by the domain controller services. In large networks running on Windows Server 2003 family operating systems, substantial resources can be required by domain controllers for performing directory replication and server authentication for clients. For this reason, many applications, such as Microsoft SQL Server and Message Queuing, recommend that, for best performance, you not install the application on domain controllers. However, if you have a very small network in which account information rarely changes and in which users do not log on and off frequently, you can use domain controllers as cluster nodes.