Dell Serial Attached SCSI 5iR Integrated and Adapter - Manual (Page 63)

Glossary 61
O
Operating System
The software that runs a computer, including
scheduling tasks, managing storage, and handling
communication with peripherals and performs basic
input/output functions, such as recognizing input
from the keyboard, sending output to the display
screen, etc. is called an operating system.
P
PCI Express (PCI-E)
PCI Express (PCI-E) is an evolutionary upgrade to
the existing Peripheral Component Interconnect
(PCI) bus. PCI-E is a serial connection that operates
more like a network than a bus. Instead of one bus
that handles data from multiple sources, PCI-E has a
switch that controls several point-to-point serial
connections. These connections fan out from the
switch, leading directly to the devices where the data
needs to go. Every device has its own dedicated
connection, so devices no longer share bandwidth like
they do on a normal bus.
PHY
The interface required to transmit and receive data
packets transferred across the serial bus. Each PHY
can form one side of the physical link in a connection
with a PHY on a different Dell-qualified SATA
device. The physical link contains four wires that form
two differential signal pairs. One differential pair
transmits signals, while the other differential pair
receives signals. Both differential pairs operate
simultaneously and allow concurrent data transmission
in both the receive and the transmit directions.
Physical Disk
A physical disk (also known as hard disk drive)
consists of one or more rigid magnetic discs rotating
about a central axle, with associated read/write heads
and electronics. A physical disk is used to store
information, (data), in a non-volatile and randomly
accessible memory space.
POST
POST, short for Power-On Self-Test is a process
performed before the operating system loads when
the computer is turned on. The POST tests various
system components, such as RAM, the physical disks,
and the keyboard.
R
RAID
Acronym for Redundant Array of Independent Disks
(originally Redundant Array of Inexpensive Disks). It
is an array of multiple independent physical disks
managed together to yield higher reliability and/or
performance exceeding that of a single physical disk.
The virtual disk appears to the operating system as a
single storage unit. I/O is expedited because several
disks can be accessed simultaneously. Redundant
RAID levels provide data protection.
ROM
Read-only memory (ROM), also known as firmware,
is an integrated circuit programmed with specific data
when it is manufactured. ROM chips are used not
only in computers, but in most other electronic items
as well. Data stored in these chips is nonvolatile i.e., it
is not lost when the power is turned off. Data stored
in these chips is either unchangeable or requires a
special operation such as flashing to change.
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