Glossary 57
Mirroring
The process of providing complete redundancy using
two physical disks, by maintaining an exact copy of
one physical disk’s data on the second physical disk.
If one physical disk fails, the contents of the other
physical disk can be used to maintain the integrity of
the system and to rebuild the failed physical disk.
N
NVDATA
This refers to non-volatile data. It is the
configuration information that is part of and is used
by the controller firmware and is stored in the flash
memory on the controller.
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.
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