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.

36 Glossary

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HP Ultrium Tape Drive manual Point-to-point connection between itself and the fabric, Connectivity technology, Is LUN1