Each single processing unit is a node canister, which is also called a node. The two nodes within the control enclosure make an I/O group that is attached to the SAN fabric. Each single processing unit is a node canister, which is also called a node. The two nodes within the enclosure make an I/O group that connects to host systems and optionally, to external storage systems.
For redundancy, nodes are deployed in pairs to make up a system. A system can have one to four pairs of nodes. Each pair of nodes is known as an I/O group. Each node can be in only one I/O group. A maximum of four I/O groups each containing two nodes is supported.
At any one time, a single node in the system manages configuration activity. This configuration node manages a cache of the configuration information that describes the system configuration and provides a focal point for configuration commands. If the configuration node fails, another node in the system takes over its responsibilities.