Eliminating Single Points of Failure in Your Network Design

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Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

You must incorporate failsafe measures within the cluster network design. To achieve this end, adhere to the following rules:

  • Configure at least two of the cluster networks for internal cluster communication to eliminate a single point of failure. A server cluster whose nodes are connected by only one network is not supported.

  • Design each cluster network so that it fails independently of other cluster networks. This requirement implies that the components that make up any two networks must be physically independent. For example, the use of a multiport network adapter to attach a node to two cluster networks does not meet this requirement if the ports share circuitry.

  • If using multihoming nodes, make sure the adapters reside on separate subnets.

  • Do not connect multiple adapters on one node to the same network; doing so does not provide fault tolerance or load balancing.

    Note

    • If a cluster node has multiple adapters attached to one network, the Cluster service will recognize only one network adapter per node per subnet.

The best way to guard against network failure in your server cluster is by teaming network adapters. By grouping network adapters on multiple ports to a single physical segment, you can provide fault tolerance to your cluster network. If a port fails — whether the failure occurs on the adapter, cable, switch port, or switch — another port takes over automatically. To the operating system and other devices on the network, this failover is transparent.

An important consideration, however, is that networks dedicated to internal server cluster communication cannot be teamed. Teaming network adapters is supported only on networks that are not dedicated to internal cluster traffic. Teaming network adapters on all cluster networks concurrently is not supported. There are alternative methods for achieving redundancy on networks that are dedicated to internal cluster traffic. These alternatives include adding a second private network, which avoids the cost of adding network adapters (however, this second network must be for intra-cluster network traffic only).

Teaming network adapters on other cluster networks is acceptable; however, if communication problems occur on a teamed network, it is recommended that you disable teaming.