HP Surestore 6.140 Tape Library - Manual (Page 197)

Appendix C C-13
Introduction to Fibre Channel
Fibre Channel Technology
Fi
bre
Ch
a
nne
l
During normal operations, device addresses do not change. Fibre
Channel addresses can only change when device communications are
disrupted. Consequently, system software does not need to spend extra
time during normal operations to keep track of device addresses.
All Fibre Channel devices are identified using their WWN. The WWN is
used by system software to locate devices independent of how they are
connected to the system so that the software does not need to be
reconfigured every time the system is reconfigured. Also, being able to
track devices helps prevent losing or damaging data by accidentally
accessing the wrong device in the system. This is a very important
requirement for the development of the SAN (Storage Area Network)
systems.
Common Problems with Fibre Channel
Fibre Channel accommodates many protocols and physical interfaces,
but problems can occur with the following:
• Physical connections
• Laser power control systems
• Error recovery
Physical Connections
Physical connection problems arise from connecting devices with
different types of cables, poor connections, damaged cables, or damaged
connectors.
ANSI controls the cable specification. The maximum distance between
devices depends on the type of cable and desired data transmission
speed. As with all electrical media, Fibre Channel copper media can
radiate RF interferences and can be affected by external RF noises.
Because of the distance limitations and noise problems, copper media is
only recommended for use inside a cabinet or rack.