Cluster Interconnect

The cluster interconnect is the physical configuration of devices that is used to transfer cluster-private communications and data service communications between cluster nodes. Because the interconnect is used extensively for cluster-private communications, it can limit performance.

Only cluster nodes can be connected to the cluster interconnect. The Sun Cluster security model assumes that only cluster nodes have physical access to the cluster interconnect.

You can set up from one to six cluster interconnects in a cluster. While a single cluster interconnect reduces the number of adapter ports that are used for the private interconnect, it provides no redundancy and less availability. If a single interconnect fails, moreover, the cluster spends more time performing automatic recovery. Two or more cluster interconnects provide redundancy and scalability, and therefore higher availability, by avoiding a single point of failure.

The cluster interconnect consists of three hardware components: adapters, junctions, and cables. The following list describes each of these hardware components.

• Adapters – The network interface cards that are located in each cluster node. Their names are constructed from a device name immediately followed by a physical-unit number, for example, qfe2. Some adapters have only one physical network connection, but others, like the qfe card, have multiple physical connections. Some adapters also contain both network interfaces and storage interfaces.

  A network adapter with multiple interfaces could become a single point of failure if the entire adapter fails. For maximum availability, plan your cluster so that the only path between two nodes does not depend on a single network adapter.

• Junctions – The switches that are located outside of the cluster nodes. Junctions perform pass-through and switching functions to enable you to connect more than two nodes. In a two-node cluster, you do not need junctions because the nodes can be directly connected to each other through redundant physical cables connected to redundant adapters on each node. Greater than two-node configurations generally require junctions.

• Cables – The physical connections that you install either between two network adapters or between an adapter and a junction.

See Chapter 4, Frequently Asked Questions for questions and answers about the cluster interconnect.