LSI Series 518 145

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	A disk array with an array management software in its host computer
Array	rather than in a disk subsystem.

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