StorageTek L180, Service Manual

Page: 247 / 266

95897 Fifth Edition A-21
External Interfaces
Fibre Channel
The library supports the following topologies with a single N_Port attachment:
• Arbitrated loop—private loop
• Arbitrated loop—public loop
The arbitrated loop provides:
• Multiple connections for devices that share a single loop
• Point-to-point connections during communications
In a Fibre Channel arbitrated loop, as with SCSI, devices must arbitrate and win
the connection before communications can begin. After a device is powered on
and initialized on the loop, it must arbitrate and win to be able to communicate
with other devices on the loop.
Private Arbitrated Loop
If the arbitrated loop is not attached to a Fibre Channel fabric, it is a private
loop. A private arbitrated loop can connect up to 126 N-type ports, and:
• Only point-to-point communication is possible between one initiator and
one target at any time. (Other links on the loop act as repeaters.)
• Both initiator and target must reside within the same loop.
While the library supports this Fibre Channel topology, StorageTek does not
recommend it. Its best implementation includes a Fibre Channel hub.
Public Arbitrated Loop
If the Fibre Channel arbitrated loop contains at least one F-type (F=Fabric) port
and is attached to a Fibre Channel fabric, it is a public loop. A public loop can
contain up to 126 N-type ports and one F-type port. If the fabric connects to
another arbitrated loop, then an initiator on one public loop might be able to
communicate with a target on another.
Fibre Channel Cable Considerations
Table A-10 lists the cable and connector specifications for the library:
Table A-10. Fibre Channel Cables and Connectors
Distance
FC-0 Code Cable Type Connector
Meters Feet
2 to 300 6.5 to 985 100-M6-SN-I 62.5 µm
Multimode
Shortwave laser
without OFC
Keyed Duplex SC
2 to 500 6.5 to 1640 100-M5-SN-I 50 µm
Multimode
Shortwave laser
without OFC
Keyed Duplex SC