IBM DS3950, Installation, User'S, And Maintenance Manual

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DMA. See direct memory access .
domain. The most significant byte in the node port
(N_port) identifier for the fibre-channel (FC) device. It
is not used in the Fibre Channel-small computer system
interface (FC-SCSI) hardware path ID. It is required to
be the same for all SCSI targets logically connected to
an Fibre Channel adapter.
drive channels. The DS4200, DS4700, and DS4800
subsystems use dual-port drive channels that, from the
physical point of view, are connected in the same way
as two drive loops. However, from the point of view of
the number of drives and enclosures, they are treated
as a single drive loop instead of two different drive
loops. A group of storage expansion enclosures are
connected to the DS3950 storage subsystems using a
drive channel from each controller. This pair of drive
channels is referred to as a redundant drive channel
pair.
drive loops. A drive loop consists of one channel from
each controller combined to form one pair of redundant
drive channels or a redundant drive loop. Each drive
loop is associated with two ports. (There are two drive
channels and four associated ports per controller.) For
the DS4800, drive loops are more commonly referred to
as drive channels. See
drive channels .
DRAM. See dynamic random access memory .
Dynamic Host Configuration Protocol (DHCP). A
protocol defined by the Internet Engineering Task Force
that is used for dynamically assigning Internet Protocol
(IP) addresses to computers in a network.
dynamic random access memory (DRAM). A storage
in which the cells require repetitive application of
control signals to retain stored data.
ECC.
See error correction coding .
EEPROM.
See electrically erasable programmable
read-only memory .
EISA. See Extended Industry Standard Architecture .
electrically erasable programmable read-only memory
(EEPROM).
A type of memory chip which can retain
its contents without consistent electrical power. Unlike
the PROM which can be programmed only once, the
EEPROM can be erased electrically. Because it can only
be reprogrammed a limited number of times before it
wears out, it is appropriate for storing small amounts
of data that are changed infrequently.
electrostatic discharge (ESD). The flow of current that
results when objects that have a static charge come into
close enough proximity to discharge.
environmental service module (ESM) canister. A
component in a storage expansion enclosure that
monitors the environmental condition of the
components in that enclosure. Not all storage
subsystems have ESM canisters.
E_port. See expansion port .
error correction coding (ECC). A method for encoding
data so that transmission errors can be detected and
corrected by examining the data on the receiving end.
Most ECCs are characterized by the maximum number
of errors they can detect and correct.
ESD. See electrostatic discharge .
ESM canister. See environmental service module canister .
automatic ESM firmware synchronization. When you
install a new ESM into an existing storage expansion
enclosure in a storage subsystem that supports
automatic ESM firmware synchronization, the firmware
in the new ESM is automatically synchronized with the
firmware in the existing ESM.
EXP. See storage expansion enclosure .
expansion port (E_port). A port that connects the
switches for two fabrics.
Extended Industry Standard Architecture (EISA).
A
bus standard for IBM compatibles that extends the
Industry Standard Architecture (ISA) bus architecture to
32 bits and allows more than one central processing
unit (CPU) to share the bus. See also
Industry Standard
Architecture .
fabric. A Fibre Channel entity which interconnects and
facilitates logins of N_ports attached to it. The fabric is
responsible for routing frames between source and
destination N_ports using address information in the
frame header. A fabric can be as simple as a
point-to-point channel between two N-ports, or as
complex as a frame-routing switch that provides
multiple and redundant internal pathways within the
fabric between F_ports.
fabric port (F_port). In a fabric, an access point for
connecting a user's N_port. An F_port facilitates N_port
logins to the fabric from nodes connected to the fabric.
An F_port is addressable by the N_port connected to it.
See also
fabric .
FC. See Fibre Channel .
FC-AL. See arbitrated loop .
feature enable identifier. A unique identifier for the
storage subsystem, which is used in the process of
generating a premium feature key. See also
premium
feature key .
Fibre Channel (FC). A set of standards for a serial
input/output (I/O) bus capable of transferring data
between two ports at up to 100 Mbps, with standards
proposals to go to higher speeds. FC supports
point-to-point, arbitrated loop, and switched topologies.
Glossary
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