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GLOSSARY
Battery Backup Module
Many modern RAID controllers are armed with a battery backup Mod-
ule (BBM). While an UPS protects most servers from power uctua-
tions or failures, a BBM provides an additional level of protection. In
the event of a power failure, a BBM supplies power to retain data in
the RAID controller’s cache, thereby permitting any potentially dirty
data in the cache to be ushed out to secondary storage when power
is restored.
BIOS
(Basic Input/Output System) software is stored on a chip and provides
an interface between the operating system and the hardware. Usually
the BIOS is built into a ROM chip installed on the motherboard so that
the BIOS will always available and not affected by disk failure.
Cache
Controller memory used to speed up data transfer to and from a disk.
Consistency Check
In RAID, check consistency veries the correctness of redundant data
in an array. For example, in a system with dedicated parity, checking
consistency means computing the parity of the data drives and com-
paring the results to the contents of the dedicated parity drive.
Driver
It is a piece of software – that is often executed in kernel mode – that
controls a hardware device. Typically drivers provide an interface by
which applications can use the device in a uniform and hardware-inde-
pendent manner.
Hot Spare
An extra physical disk drive in a RAID conguration that controller can
use to automatically rebuild a system drive when another drive fails.
The hot spare drive must have at least as mush capacity as the largest
disk drive in the array or the rebuild may not start.