Glossary
This glossary defines terms used in this guide or related to this product and is not a
comprehensive glossary of computer terms.
A
active member of
a virtual disk
family
A simulated disk drive created by the controllers as storage for one or more hosts. An active
member of a virtual disk family is accessible by one or more hosts for normal storage. An active
virtual disk member and its snapshot, if one exists, constitute a virtual disk family. An active
member of a virtual disk family is the only necessary member of a virtual disk family.
See also virtual disk,virtual disk copy,virtual disk family, and snapshot .
adapter See controller.
AL_PA Arbitrated loop physical address. A 1-byte value the arbitrated loop topology uses to identify the
loop ports. This value becomes the last byte of the address identifier for each public port on the
loop.
allocation policy The storage system rules that govern how virtual disks are created. There are two rules:
• Allocate Completely—The space a virtual disk requires on the physical disks is reserved,
even if the virtual disk is not currently using the space.
• Allocate on Demand—The space a virtual disk requires on the physical disks is not reserved
until needed.
ALUA Asymmetric logical unit access. Operating systems that support asymmetric logical unit access
work with the array’s active/active functionality to enable any virtual disk to be accessed through
either of the array’s two controllers.
ambient
temperature
The air temperature in the area where a system is installed. Also called intake temperature or
room temperature.
ANSI American National Standards Institute. A non-governmental organization that develops standards
(such as SCSI I/O interface standards and Fibre Channel interface standards) used voluntarily
by many manufacturers within the United States.
arbitrated loop A Fibre Channel topology that links multiple ports (up to 126) together on a single shared simplex
medium. Transmissions can only occur between a single pair of nodes at any given time.
Arbitration is the scheme that determines which node has control of the loop at any given moment
arbitrated loop
physical address
See AL_PA.
arbitrated loop
topology
See arbitrated loop.
array synonym of storage array, storage system, and virtual array. A group of disks in one or more
disk enclosures combined with controller software that presents disk storage capacity as one or
more virtual disks.
array controller See controller.
array controller
failover
The process that takes place when one controller assumes the workload of a failed companion
controller.
asynchronous Events scheduled as the result of a signal requesting the event or that which is without any specified
time relation.
B
backplane An electronic printed circuit board that distributes data, control, power, and other signals among
components in an enclosure.
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.
132 Glossary
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