Managing RAID on Linux

Motherboards and the PCI Bus

Motherboards provide a way to interconnect the various components that make up a computer (memory, processors, and peripherals). Every motherboard has separate buses for communicating between these varied components. Disk controllers and, in turn, hard disks, communicate with the CPU and memory using the I/O bus, also called the data bus. The I/O bus is a standard interface through which peripheral cards (disk controllers, graphics adapters, network cards, etc.) can interface between peripherals (hard disks, monitors, Ethernet networks, etc.) and the CPU and memory.

The Peripheral Component Interconnect (PCI) bus is the most common data bus available today. In recent years, it has usurped the ubiquity of the now outdated Industry Standard Architecture (ISA) bus. Although ISA motherboards are still common, new motherboard purchases typically use the PCI bus. For backward compatibility, the PCI bus can handle ISA peripheral cards through the use of bridging, and many PCI motherboards provide an ISA slot for use with legacy cards.

Bus-width and bus-speed

The speed of the I/O bus is determined by two factors: bus-width and bus-speed. Bus-width describes how many bytes of data can be sent down the bus at a time. Bus-speed specifies how many times per second data can be transferred through the bus. Bus-width is measured in bits, and all motherboards support bus-widths in multiples of bytes. ISA motherboards support bus-widths of 8 and 16 bits (1 or 2 bytes), ...