LSI Corporation
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6Gb/s MegaRAID SAS RAID Controllers User Guide
August 2012
Glossary
M
main memory The part of computer memory that is directly accessible by the CPU (usually synonymous
with RAM).
N
NVRAM Acronym for nonvolatile random access memory. An EEPROM (electronically erasable read-only
memory) chip that stores configuration information. See EEPROM.
P
PCI Acronym for peripheral component interconnect. A high-performance, local bus specification
that allows the connection of devices directly to computer memory. The PCI Local Bus allows
transparent upgrades from 32-bit data path at 33 MHz to 64-bit data path at 33 MHz, and from
32-bit data path at 66 MHz to 64-bit data path at 66 MHz.
PCI Express Acronym for peripheral component interconnect Express. A high-performance, local bus
specification that permits the connection of devices directly to computer memory. PCI Express is
a two-way, serial connection that transfers data on two pairs of point-to-point data lines. PCI
Express goes beyond the PCI specification in that it is intended as a unifying I/O architecture
for various systems: desktops, workstations, mobile, server, communications, and
embedded devices.
peripheral devices A piece of hardware (such as a video monitor, drive, printer, or CD-ROM) used with a computer
and under the control of the computer. SCSI peripherals are controlled through a MegaRAID SAS
RAID controller (host adapter).
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 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.
R
RAID Acronym for Redundant Array of Independent Disks (originally Redundant Array of Inexpensive
Disks). An array (group) of multiple independent drives managed together to yield higher
reliability, performance, or both exceeding that of a single drive. The RAID array appears to the
controller as a single storage unit. I/O is expedited because several drives can be accessed
simultaneously. Redundant RAID levels (RAID levels 1, 5, 6, 10, 50, and 60) provide
data protection.
RAID levels A set of techniques applied to drive groups to deliver higher data availability, performance
characteristics, or both to host environments. Each virtual drive must have a RAID level
assigned to it.
S
SAS Acronym for Serial Attached SCSI. A serial, point-to-point, enterprise-level device interface that
leverages the proven SCSI protocol set. The SAS interface provides improved performance,
simplified cabling, smaller connections, lower pin count, and lower power requirements when
compared to parallel SCSI. SAS controllers leverage a common electrical and physical connection
interface that is compatible with Serial ATA.
The SAS controllers support the ANSI Serial Attached SCSI Standard, Version 2.0. In addition, the
controller supports the Serial ATA III (SATA III) protocol defined by the Serial ATA Specification,
Version 3.0. Supporting both the SAS interface and the SATA III interface, the SAS controller is a
versatile controller that provides the backbone of both server and high-end workstation
environments. Each port on the SAS RAID controller supports SAS devices, SATA devices, or both.
SAS device Any device that conforms to the SAS standard and is attached to the SAS bus by a SAS cable. This
includes SAS RAID controllers (host adapters) and SAS peripherals.
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