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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 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 standard. It uses the same 8-bit bus as the
original SCSI-1, but runs at up to 10 Mbytes (double the speed of SCSI-
1.)
Firmware Software stored in read-only memory (ROM) or Programmable ROM
(PROM). Firmware often controls 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.
Format The process of writing zeros to all data fields in a physical drive (disk
drive) to map out unreadable or bad sectors. Because most disk drives
are factory formatted, formatting is usually only done if a hard disk
generates many media errors.
GByte Gigabyte. Shorthand for 1,000,000,000 (10 to the ninth power) bytes.
One Gbyte is equivalent to 1,000 Mbytes.
Host-based
Array
A disk array with an array management software in its host computer
rather than in a disk subsystem.