LSI Nytro MegaRAID 8120-4i User's Guide download pdf (Page 21)

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LSI Nytro MegaRAID Application Acceleration Card User Guide

August 2012

Glossary

main memory The part of computer memory that is directly accessible by the CPU (usually synonymous with RAM).

MSM MegaRAID Storage Manager software

PCI Express

(PCIe)

Acronym for peripheral component interconnect Express. A high- performance, local bus specification that

allows 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 SAS MegaRAID SAS RAID controller (host

adapter).

PSBRAM Pipelined synchronous burst static random access memory

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.

RAID 0 Uses striping to provide high data throughput, especially for large files in an environment that does not

require fault tolerance.

RAID 1 Uses mirroring so that data written to one drive is simultaneously written to another drive. RAID 1 is good for

small databases or other applications that require small capacity but complete data redundancy.

RAID 5 Uses disk striping and parity data across all drives (distributed parity) to provide high data throughput,

especially for small random access.

RAID 6 Uses distributed parity, with two independent parity blocks per stripe, and disk striping. A RAID 6 virtual

drive can survive the loss of any two drives without losing data. A RAID 6 drive group, which requires a

minimum of three drives, is similar to a RAID 5 drive group. Blocks of data and parity information are written

across all drives. The parity information is used to recover the data if one or two drives fail in the drive group.

RAID 10 A combination of RAID 0 and RAID 1, consists of striped data across mirrored spans. A RAID 10 drive group is

a spanned drive group that creates a striped set from a series of mirrored drives. RAID 10 allows a maximum

of 8 spans. You must use an even number of drives in each RAID virtual drive in the span. The RAID 1 virtual

drives must have the same stripe size. RAID 10 provides high data throughput and complete data

redundancy but uses a larger number of spans.

RAID 50 A combination of RAID 0 and RAID 5, uses distributed parity and disk striping. A RAID 50 drive group is a

spanned drive group in which data is striped across multiple RAID 5 drive groups. RAID 50 works best with

data that requires high reliability, high request rates, high data transfers, and medium-to-large capacity.

NOTE Having virtual drives of different RAID levels, such as RAID 0 and RAID 5, in the same drive group is not

allowed. For example, if an existing RAID 5 virtual drive is created out of partial space in an array, the next

virtual drive in the array has to be RAID 5 only.

RAID 60 A combination of RAID 0 and RAID 6, uses distributed parity, with two independent parity blocks per stripe in

each RAID set, and disk striping. A RAID 60 virtual drive can survive the loss of two drives in each of the RAID

6 sets without losing data. RAID 60 works best with data that requires high reliability, high request rates, high

data transfers, and medium-to-large capacity.

NOTE The MegaSR controller supports the standard RAID levels—RAID 0, RAID 1, RAID 5, and RAID 10. The

MegaSR controller comes in two variants, SCU and AHCI, both supporting a maximum of eight physical

drives. A maximum of eight virtual drives can be created (using RAID 0, RAID 1, RAID 5, and RAID 10 only) and

controlled by the MegaSR controller. One virtual drive can be created on an array (a maximum of eight if no

other virtual drives are already created on the MegaSR controller), or you can create eight arrays with one

virtual drive each. However, on RAID10, you can create only one virtual drive on a particular array.

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LSI Nytro MegaRAID 8120-4i User's Guide Page 21

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