Owner's manual

Glossary 69
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.
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