HP StorageWorks 4400 User Manual page 119

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
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 Fibre Channel connector on a Fibre Channel device.
port-colored A convention of applying 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 See PDM.
module
power distribution See PDU.
unit
power supply An element that develops DC voltages for operating the storage system elements
from either an AC or DC source.
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.
pushbutton A button that is engaged or disengaged when it is pressed.
quiesce
The act of rendering bus activity inactive or dormant. For example, "quiesce the
SCSI bus operations during a device warm-swap."
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 1.75 inches (44.45 mm) and based on EIA's Standard RS310C. For
example, a 3U unit is 5.25inches (133.35 mm) high, and a 4U unit is 7.0inches
(177.79 mm) high.
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
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