Two-Node Networks

Figure 1-2 shows how two nodes in a Sun HPC 3.0 cluster can be connected via an SCI network. The SCI adapter card in one node is connected directly to an SCI adapter card in the other node. There is no intervening SCI switch, which is the usual connection scheme for two-node networks.

If each node has two SCI adapter cards, messages can be striped across the two network interfaces. This is illustrated in lower schematic in "Connecting SCI Adapter Cards in a Two-Node Network".

Figure 1-2 Two-Node SCI Interconnection, Without Striping

If you expect to add a node to a two-node network at a later time, you may want to connect the two nodes through a switch now, even though the switch is not needed. This would simplify the process of adding a third node later on. The chief disadvantage to using a switch in a two-node network is the latency it adds to the communication path between the nodes.

This alternate connection scheme is discussed further in "Connecting SCI Adapter Cards in a Two-Node Network".