Device nodes

Devices are organized into clusters known as nodes. Each node is a logical subsystem of devices, where lower-level devices have a dependency on upper-level devices in child-parent relationships.

For example, the system node is the highest of all nodes and consists of all the physical devices in the system. The system device is the top of the node and below that are the bus and adapters that have a dependency on the higher-level system device. At the bottom of the hierarchy are devices to which no other devices are connected. These devices have dependencies on all devices above them in the hierarchy.

At startup time, parent-child dependencies are used to configure all devices that make up a node. Configuration occurs from the top node down and any device having a dependency on a higher-level device is not configured until the higher-level device is configured.

The AIX® operating system supports the multiple path I/O (MPIO) feature. If a device has an MPIO-capable device driver, it can have more than one parent within this hierarchy, which allows multiple, simultaneous communication paths between the device and a given machine or logical partition within a machine.