American Megatrends MegaRAID Express 500 - Manual (Page 112)

MegaRAID Express 500 Hardware Guide 98
Glossary, Continued
Reconstruct The act of remaking a logical drive after changing RAID levels or adding a
physical drive to an existing array.
Redundancy The provision of multiple interchangeable components to perform a single
function to cope with failures or errors. Redundancy normally applies to
hardware; a common form of hardware redundancy is disk mirroring.
Replacement Disk A disk available to replace a failed member disk in a RAID array.
Replacement Unit A component or collection of components in a disk subsystem that are always
replaced as a unit when any part of the collection fails. Typical replacement units
in a disk subsystem includes disks, controller logic boards, power supplies, and
cables. Also called a hot spare.
SAF-TE SCSI Accessed Fault-Tolerant Enclosure. An industry protocol for managing
RAID enclosures and reporting enclosure environmental information.
SCSI (Small Computer System Interface) A processor-independent standard for
system-level interfacing between a computer and intelligent devices, including
hard disks, floppy disks, CD-ROM, printers, scanners, etc. SCSI can connect up
to 7 devices to a single adapter (or host adapter) on the computer's bus. SCSI
transfers eight or 16 bits in parallel and can operate in either asynchronous or
synchronous modes. The synchronous transfer rate is up to 40 MB/s. SCSI
connections normally use single ended drivers, as opposed to differential drivers.
The original standard is now called SCSI-1 to distinguish it from SCSI-2 and
SCSI-3, which include specifications of Wide SCSI (a 16-bit bus) and Fast SCSI
(10 MB/s transfer).
SCSI Channel MegaRAID controls the disk drives via SCSI-2 buses (channels) over which the
system transfers data in either Fast and Wide or Ultra SCSI mode. Each adapter
can control up to three SCSI channels. Internal and external disk drives can be
mixed on channels 0 and 1, but not on channel 2.
Cont’d