American Megatrends MegaRAID Express 500 - Manual (Page 107)

Glossary 93
Glossary, Continued
Disk Striping A type of disk array mapping. Consecutive stripes of data are mapped round-
robin to consecutive array members. A striped array (RAID Level 0) provides
high I/O performance at low cost, but provides lowers data reliability than any of
its member disks.
Disk Subsystem A collection of disks and the hardware that connects them to one or more host
computers. The hardware can include an intelligent controller or the disks can
attach directly to a host computer I/O a bus adapter.
Double Buffering A technique that achieves maximum data transfer bandwidth by constantly
keeping two I/O requests for adjacent data outstanding. A software component
begins a double-buffered I/O stream by issuing two requests in rapid sequence.
Thereafter, each time an I/O request completes, another is immediately issued. If
the disk subsystem is capable of processing requests fast enough, double
buffering allows data to be transferred at the full-volume transfer rate.
Failed Drive A drive that has ceased to function or consistently functions improperly.
Fast SCSI A variant on the SCSI-2 bus. It uses the same 8-bit bus as the original SCSI-1,
but runs at up to 10MB (double the speed of SCSI-1.)
Firmware Software stored in read-only memory (ROM) or Programmable ROM (PROM).
Firmware is often responsible for the behavior of a system when it is first turned
on. A typical example would be a monitor program in a computer that loads the
full operating system from disk or from a network and then passes control to the
operating system.
FlexRAID Power Fail Option The FlexRAID Power Fail option allows a reconstruction to restart
if a power failure occurs. This is the advantage of this option. The disadvantage
is, once the reconstruction is active, the performance is slower because an
additional activity is added.
Cont’d