User Manual

Glossary
207Enterprise Virtual Array 3000 User Guide
backplane
An electronic printed circuit board that distributes data, control, power, and other signals to
element connectors.
bad block
A data block that contains a physical defect.
bad block replacement
A replacement routine that substitutes defect-free disk blocks for those found to have defects.
This process takes place in the controller and is transparent to the host.
bail lock
Part of the power supply AC receptacle that engages the AC power cord connector to ensure
that the cord cannot be accidentally disconnected.
baud
The maximum rate of signal state changes per second on a communication circuit. If each
signal state change corresponds to a code bit, then the baud rate and the bit rate are the same. It
is also possible for signal state changes to correspond to more than one code bit so the baud
rate may be lower than the code bit rate.
bay
The physical location of an element, such as a drive, I/O module, EMU or power supply in a
drive enclosure. Each bay is numbered to define its location.
bidirectional
Also called Bi-Di. The movement of optical signals in opposite directions through a common
fiber cable such as the data flow path typically on a parallel printer port. A parallel port can
provide two-way data flow for disk drives, scanning devices, FAX operations and even parallel
modems.
block
Also called a sector. The smallest collection of consecutive bytes addressable on a disk drive.
In integrated storage elements, a block contains 512 bytes of data, error codes, flags, and the
block address header.
blower
A variable speed airflow device that pulls air into an enclosure or element. It usually pulls air
in from the front and exhausts the heated air out the rear.
cabinet
An alternate term used for a rack.