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Glossary
active termination,
regulated
Terminates the SCSI bus with a series of resistors tied to +5 volts. The terminator is
labeled Regulated but is often referred to as an Active Terminator.
active-active
controllers
A pair of components, such as storage controllers in a failure-tolerant RAID array that
share a task or set of tasks when both are functioning normally. When one component of
the pair fails, the other takes the entire load. Dual active controllers (also called dual-
active controllers) are connected to the same set of devices and provide a combination of
higher I/O performance and greater failure tolerance than a single controller.
ANSI American National Standards Institute
automatic rebuild A process where data is automatically reconstructed after a drive failure and written to a
standby (spare) drive. An automatic rebuild will also occur when a new drive is installed
manually in place of a failed drive. If the rebuild process is interrupted by a reset, use the
Rebuild command on the Array Administration menu to restart the rebuilding process.
background rate The background rate is the percentage of available array controller CPU time assigned to
array administration activities, such as rebuilding failed drives, checking parity, and
initialization. If the background rate is set to 100%, the array administration activities
have a higher priority than any other array activity. At 0%, the array administration
activity is done only if there is no other activity on the array controller.
bandwidth A measure of the capacity of a communication channel, usually specified in MB/second.
cache Memory on the RAID controller card, which permits intermediate storage of, read and
write data without physically reading/writing from/to the disk, which can increase overall
performance under certain conditions.
caching Allows data to be stored in a pre-designated area of a disk or RAM (random access
memory). Caching is used to speed up the operation of RAID arrays, disk drives,
computers and servers, or other peripheral devices.
CH Channel
channel Any path used for the transfer of data and control information between storage devices
and a storage controller or I/O adapter. Also refers to one SCSI bus on a disk array
controller. Each disk array controller provides at least one channel.
CISPR International Special Committee on Radio Interference
CLI Command line interface.
concatenated
channel
Inside the same drive array enclosure, a single contiguous drive channel supporting 12
drives concurrently
device name Software device address that identifies the controller/LUN, such as cXtYdZs0, where X is
the host bus adapter, Y is the controller, and Z is the LUN. s0 slice number is used by the
system, not by RAID Manager.
disk array Two or more drives configured as a Drive Group (see next).
drive group A physical set of drives configured as an array. Drive groups are defined during
configuration.
EMU Event Monitoring Unit
expansion drive
array
An enclosure containing a group of drives, power supplies, cooling fans, I/O cards, and
mid-planes (no RAID controller/controllers); generally, an external drive array that is used
to daisy chain to an existing hardware based RAID configuration.
failover A mode of operation for failure-tolerant arrays in which a component has failed and its
function has been assumed by a redundant component.
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