HP 6400.8400 Enterprise Virtual Array - Manual (Page 144)

PDM Power distribution module. A thermal circuit breaker-equipped power strip that distributes power
from a PDU to HP Enterprise Storage System elements.
PDU Power distribution unit. The rack device that distributes conditioned AC or DC power within a
rack.
petabyte A unit of storage capacity that is the equivalent of 2
50
, 1,125,899,906,842,624 bytes or 1,024
terabytes.
physical disk A disk drive mounted in a drive enclosure that communicates with a controller pair through the
device-side Fibre Channel loops. A physical disk is hardware with embedded software, as opposed
to a virtual disk, which is constructed by the controllers. Only the controllers can communicate
directly with the physical disks.
The physical disks, in aggregate, are called the array and constitute the storage pool from which
the controllers create virtual disks.
physical disk array See array.
port A physical connection that allows data to pass between a host and a disk array.
port-colored Pertaining to the application of the color of port or red wine to a CRU tab, lever, or handle to
identify the unit as hot-pluggable.
port_name A 64-bit unique identifier assigned to each Fibre Channel port. The port_name is communicated
during the login and port discovery processes.
power distribution
module See PDM.
power distribution
unit See PDU.
power supply An element that develops DC voltages for operating the storage system elements from either an
AC or DC source.
preferred address An AL_PA which a node port attempts to acquire during loop initialization.
preferred path A preference for which controller of the controller pair manages the virtual disk. This preference
is set by the user when creating the virtual disk. A host can change the preferred path of a virtual
disk at any time. The primary purpose of preferring a path is load balancing.
protocol The conventions or rules for the format and timing of messages sent and received.
Q
quiesce The act of rendering bus activity inactive or dormant. For example, “quiesce the SCSI bus
operations during a device warm-swap.”
R
rack A floorstanding structure primarily designed for, and capable of, holding and supporting storage
system equipment. All racks provide for the mounting of panels per Electronic Industries Alliance
(EIA) Standard RS310C.
rack-mounting unit A measurement for rack heights based upon a repeating hole pattern. It is expressed as “U”
spacing or panel heights. Repeating hole patterns are spaced every 44.45 mm (1.75 inches)
and based on EIA’s Standard RS310C. For example, a 3U unit is 133.35 mm (5.25 inches)
high, and a 4U unit is 177.79 mm (7.0 inches) high.
read ahead
caching A cache management method used to decrease the subsystem response time to a read request
by allowing the controller to satisfy the request from the cache memory rather than from the disk
drives.
read caching A cache method used to decrease subsystem response times to a read request by allowing the
controller to satisfy the request from the cache memory rather than from the disk drives. Reading
data from cache memory is faster than reading data from a disk. The read cache is specified as
either On or Off for each virtual disk. The default state is on.
reconstruction The process of regenerating the contents of a failed member data. The reconstruction process
writes the data to a spare set disk and incorporates the spare set disk into the mirrorset, striped
mirrorset or RAID set from which the failed member came.
144 Glossary