RAID

Redundant Array of Independent Disks. An array of multiple independent

 

hard disk drives that yields better performance than a Single Large

 

Expensive Disk (SLED). A RAID disk subsystem improves I/O

 

performance on a server using only a single drive. The RAID array

 

appears to the host server as a single storage unit. I/O is expedited

 

because several disks can be accessed simultaneously.

RAID 0

Provides block “striping” across multiple drives, yielding higher

 

performance than is possible with individual drives. This level does not

 

provide any redundancy.

RAID 1

Drives are paired and mirrored. All data is 100 percent duplicated on a

 

drive of equivalent size.

SCSI Bus

A host adapter and one or more SCSI devices connected by cables in a

 

linear configuration. The host adapter may exist anywhere on the bus,

 

allowing connection of both internal and external SCSI devices. A system

 

may have more than one SCSI bus by using a multichannel host adapter

 

or by using multiple host adapters.

SCSI Device

Any device that conforms to the SCSI standard and is attached to the

 

SCSI bus by a SCSI cable. This includes SCSI host adapters, SCSI disk

 

drives, SCSI CD-ROM drives, and so on.

SCSI ID

An identifier that addresses specific devices on the SCSI bus and

 

determines device selection when multiple devices contend for ownership

 

of the SCSI bus. Wide SCSI buses support SCSI IDs 0–15, and narrow

 

SCSI buses support SCSI IDs 0–7. A device gains ownership of the bus

 

according to the priority of its SCSI ID. The order of priority, from highest

 

to lowest, is: 7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, 8. The host

 

adapter is usually set to the highest priority SCSI ID, which is SCSI ID 7.

Single-Ended

A hardware specification for connecting SCSI devices. It references each

SCSI

SCSI signal to a common ground. In contrast, differential SCSI uses a

 

separate ground for each signal.

SureLINK

The domain validation method developed and used by LSI Logic.

 

SureLINK Domain Validation provides three levels of integrity checking:

 

Basic (level 1), Enhanced (level 2), and Margined (level 3).

Ultra SCSI

A standard for SCSI data transfers. It allows a transfer rate of up to

 

20 Mbytes/s over an 8-bit SCSI bus and up to 40 Mbytes/s over a 16-bit

 

SCSI bus.

Glossary of Terms

A-3

Version 2.2

Copyright © 2002–2004 by LSI Logic Corporation. All rights reserved.