compression A procedure in which data is transformed by the removal of redundant information
in order to reduce the number of bits required to represent the data.
compression ratio A measure of how much compression has occurred, defined as the ratio of the
amount of uncompressed data to the amount of compressed data into which it
is transformed. The LTO-DC algorithm can typically achieve a compression ratio
of between 2:1 and 4:1 depending on the nature of the data.
decompression A procedure in which the original data is generated from compressed data.
DFA Direct Fabric Attach. The connection between an N_port and an F_port.
ECMA European Computer Manufacturers Association. The European equivalent of
ANSI.
EOD End Of Data. An area that signifies the end of the valid data. If new data is
written over a larger quantity of old data, it is possible for data to exist after
EOD, but because it is after EOD, this old data is no longer valid.
EOM End Of Media format. The last usable point on the tape.
EW-EOM Early Warning End Of Media. A physical mark or a device-computed position
on the tape that tells the drive that it is approaching EOM.
F_port Fabric port. A port on a fabric switch operating according to point-to-point
topology, to which N_ports may be directly connected. An F_port uses the address
identifier FFFFFEh.
fabric See switched fabric
fabric zoning Isolation of two separate switched fabric (FC_SW) zones by the switch.
FC See fibre channel
FC_FLA Fibre Channel Fabric Loop Attach. An ANSI standard that describes the rules by
which NL_ports and FL_ports communicate with each other.
FC_GS Fibre Channel Generic Service. An ANSI standard that describes services such
as Directory Service that allow a host to identify which storage devices are
available and what their addresses are.
FC_SW Fibre Channel Switch Fabric. An ANSI standard that describes how fibre channel
switches are required to behave.
See also switched fabric
FC-AL Fibre Channel Arbitrated Loop. An ANSI standard that describes how several
Fibre Channel ports can share a single communication ring. Using optical fiber
to connect devices, FC-AL is compatible with SCSI for high-performance storage
systems.
See also arbitrated loop[
FCP Fibre Channel Protocol. There are three: arbitrated loop, point-to-point and
switched fabric.
fibre channel Fibre Channel provides an inexpensive yet expendable means of quickly
transferring data between workstations, mainframes, supercomputers, desktop
computers, storage devices, displays and other peripherals. Although it is called
Fibre Channel, its architecture represents neither a channel nor a real network
Glossary160
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