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 fluctua- 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 flushed 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 verifies 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
Hot Spare
An extra physical disk drive in a RAID configuration 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.
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