188 GlossaryPDU — Power distribution unit. A power source with multiple power outlets thatprovides electrical power to servers and storage systems in a rack.peripheral — An internal or external device, such as a diskette drive or keyboard,connected to a system.pixel — A single point on a video display. Pixels are arranged in rows and columns tocreate an image. A video resolution, such as 640 x 480, is expressed as the number ofpixels across by the number of pixels up and down.POST — Power-on self-test. Before the operating system loads when you turn on yoursystem, the POST tests various system components such as RAM and hard drives.processor — The primary computational chip inside the system that controls theinterpretation and execution of arithmetic and logic functions. Software written forone processor must usually be revised to run on another processor. CPU is a synonymfor processor.PSU — Power supply unit.PXE — Preboot eXecution Environment. A way of booting a system via a LAN(without a hard drive or bootable diskette).QPI— QuickPath Interconnect. The bus interface between the processors andbetween the processors and the IOH chip.RAID — Redundant array of independent disks. A method of providing dataredundancy. Some common implementations of RAID include RAID 0, RAID 1, RAID5, RAID 10, RAID 50, and RAID 60. See also mirroring and striping.RAM — Random-access memory. The system’s primary temporary storage area forprogram instructions and data. Any information stored in RAM is lost when you turnoff your system.RDIMM — A registered DDR3 memory module.readme file — A text file, usually shipped with software or hardware, that containsinformation supplementing or updating the product’s documentation.read-only file — A read-only file is one that you are prohibited from editing ordeleting.ROM — Read-only memory. Your system contains some programs essential to itsoperation in ROM code. A ROM chip retains its contents even after you turn off yoursystem. Examples of code in ROM include the program that initiates your system’sboot routine and the POST.ROMB — RAID on motherboard.SAN — Storage Area Network. A network architecture that enables remote network-attached storage devices to appear to a server to be locally attached.
