Sun Microsystems StorageTek, Руководство по планированию системы

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96257 Sun Confidential: Internal Only C-89
Revision A
digital . Information stored in binary form that a computer
recognizes. For computing use, text, graphics, and
sound are stored as digital bits represented by a 0 or 1.
Contrast with analog.
dimmed text . Dimmed or grayed-out text that appears
on a GUI menu and indicates an option is unavailable
because the system is not in the mode to use that func-
tion, or because software for that function is not installed.
Available options are typically displayed in undimmed
black text.
director . A logical entity that interfaces host channels to
a disk device. See also multipath storage director.
disk array . See dual-redundancy disk array.
disk array capacity . Formatted physical capacity of an
array, exclusive of capacity on redundancy/parity drives
or spare drives.
disk array controller . In VTSS, a control unit that imple-
ments storage management functions and provides in-
terface intelligence between hosts or network devices
and VTSS arrays.
disk drive . An electromagnetic mechanical device that
provides physical data storage on magnetic disk media.
DLF . See Download Facility.
DLT . Digital Linear Tape.
DMA . Direct Memory Access.
DMGR . See Diagnostic Manager.
DNS . Domain Name Server.
download . To receive files or data from one storage de-
vice or computer to another. Contrast with upload.
Download Facility (DLF) . A VTSS facility that formats
event log data and connects to a RRC PC to offload
event log and MIM information as directed by the VTSS
PSA facility and subsystem internal timers.
drain . A process that gradually moves data stored from
an individual drive, drive array, or entire array unit to al-
low for eventual nondisruptive deinstallation of the
drive(s) or unit.
drive reconstruction . See device reconstruction.
driver . A software routine that controls or regulates a
hardware device.
DSP . Digital signal processor.
dual copy . A function of VTSS nonvolatile storage that
maintains two functionally identical copies of designated
disk volumes in a logical subsystem, and automatically
updates both copies each time a write operation is is-
sued to a logical volume.
dual-redundancy disk array . In VSM, a logical grouping
of physical disk storage devices on a VTSS. In an array
five disk drives are reserved for user data, and two are
used for redundancy/parity data. Dual-redundancy ar-
rays allow for real time automatic recovery of data on up
to two failed devices within an array.
duplex . Bidirectional; a two-fiber or two-element cable
that provides two-way data transmission, i.e., it can si-
multaneously send and receive data. Contrast with sim-
plex.
duplexing . In VSM, the process of writing a virtual tape
volume (VTV) on two discrete multi-volume cartridges
(MVCs).
Dynamic Configuration . A VTSS feature that allows
channel interfaces and up to 1024 functional volumes to
be defined and/or altered. Allows the functional configu-
ration of a VTSS to be determined by user requirements
rather than by available physical devices.
Dynamic Director . A VTSS feature that allows dynamic
switching of ESCON director links between the VTSS
and RTDs for optimum system performance.
dynamic mapping . A VTSS mapping technique that dy-
namically alters the correspondence between a function-
al track and its location on physical devices, thereby
avoiding ‘update-in-place’, a major performance bottle-
neck in conventional RAID architectures. See also map-
ping. Contrast with fixed mapping.
E
earth grounding . An electrical connection to the earth
that is used to drain electrostatic charge from personnel
and equipment.
EC . Engineering Change.
ECA . ESCON channel adapter.
ECAM . Extended Control and Monitoring. A VTSS com-
munications protocol that permits communication be-
tween ExPR and the VTSS.
ECAM device . A functional host device number over
which ExPR-based communication takes place between
a controller and host CPU(s).
ECAMT . Extended Control and Monitoring for Tape.
ECAMT device . A functional device over which VTCS
communication between the VTSS disk array controller
and the host CPU(s) takes place.
ECC . See error correction code.
ECN . Engineering Change Notice.
EDAC . Error detection and correction. A system that de-
tects and corrects errors during data transfers.
EEPROM . Electronically Erasable Programmable Read-
Only Memory.
electromagnetic interference (EMI) . Leakage of radia-
tion from a high-frequency energy transmission source
that can cause interference to equipment or radio servic-
es. National and international regulatory agencies set
limits for EMI emissions. Class A limits apply to equip-
ment for industrial use; Class B limits apply to equipment
for non-commercial residential use.
EPO . Emergency Power Off. A safety switch on a ma-
chine or in a data center that allows a user to immediate-
ly power down a machine or a data center power supply
by cutting off the external source power.
EMI . See electromagnetic interference.
EMIF . ESCON Multiple Image Facility
enterprise . A large-scale, organization-wide computer
network that may include web-based, client-server, and
mainframe computing technologies.
Enterprise Systems Connection (ESCON) . (1) A set of
fiber optic-based products and services developed by
IBM that allows devices within a storage environment to
be dynamically configured. (2) A channel-to-control unit
I/O interface that uses optical cables as a transmission
medium.