HP Ultrium Tape Drive - Manual (Page 36)

Glossary 36
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
topology. It allows for an active intelligent interconnection scheme, called a fabric,
to connect devices. All a Fibre Channel port has to do is to manage a simple
point-to-point connection between itself and the fabric.
Several common ULPs (Upper Level Protocols) including IP and SCSI can run on
Fibre Channel, merging high-speed I/O and network functionality in a single
connectivity technology.
filemark A mark written by the host to the tape that can be searched for, often using the
drive’s fast-search capability. It does not necessarily separate files. It is up to the
host to assign a meaning to the mark.
immediate mode A mode of responding to SCSI commands where the drive or other peripheral
does not wait until the command has finished before returning status information
back to the host. For writing filemarks, Immediate mode can significantly improve
the performance of systems that do not set the Immediate bit when sending a SCSI
WRITE FILEMARKS command. On the other hand, data is not flushed to tape in
response to a filemark command.
infinite flush By default, the buffer in the drive is flushed every 5 seconds. Infinite flush avoids
frequent starting and stopping of the mechanism when using a very slow
application. It also avoids losing capacity through the flushing of partly written
groups. On the other hand, infinite flush means that data can remain in the buffer
for very long periods of time, and could be lost in the event of a power failure.
LUN Logical Unit Number. A unique number by which a device is identified on the SCSI
bus. A tape drive has a fixed LUN of 0. In an autoloader, the changer mechanism
is LUN1.
SAN Storage Area Network. A dedicated, high-speed network that establishes a direct
connection between storage elements and servers. The hardware that connects
workstations and servers to storage devices in a SAN is referred to as a fabric. The
SAN fabric enables any-server-to-any-storage device connectivity through the use
of Fibre Channel switching technology.
SCSI Small Computer System Interface—a standard command specification and
command set that enables computers and peripherals to communicate with each
other. HP’s Ultrium drives adhere to the SCSI-3 specification and support all
features required by that standard.