Appendix C Driver Layers

Figure C-1 illustrates the driver layers that are used when AP controls disk devices.

Figure C-1 AP Disk Driver Layers

A user process references a metadisk, which provides access to the AP disk meta driver. The AP disk meta driver controls two instances of the physical disk driver which, in turn, controls two instances of the nexus driver (or controller driver). The nexus driver controls the physical device.

Figure C-2 illustrates the driver layers that are used when AP controls networks.

Figure C-2 AP Network Driver Layers

A user process references a metanetwork, which provides access to the stream head. The AP network meta driver is inserted into the stream between the high-level read/write processing components and the physical driver routines.