4.5Configuring the Fibre Channel Loop ID
The Id Mode must be configured for either “Soft” or “Fixed” addressing. Using “Soft” addressing, the Fibre Channel Option connects to an arbitrated loop using the first available AL_PA, scanning from the highest valid address to the lowest. Using “Fixed” addressing, the user selects a specific arbitrated loop address (AL_PA) to connect with. If the selected address is not available, the Fibre Channel Option will connect with the first available address it finds. The use of “Soft” or “Fixed” addressing is based on the user’s installation requirements.
Soft addressing can be configured when address conflicts are not likely. If the Fibre Channel Option is connected directly to the computer’s HBA (Host Bus Adapter), the selection of a specific Loop Id is not usually required. For example, Emulex HBA driv- ers scan for an available address starting from the low Fibre Channel address range. The FCO begins scanning for an available address starting from the high Fibre Chan- nel address range. This avoids address conflicts and the FCO Loop Id will be assigned the same value each time it is restarted.
Hard addressing should be configured if address conflicts can occur. This can happen if the FCO is connected to a Fibre Channel Hub. Since many HBA drivers map the Fi- bre Channel Loop Id to a SCSI Bus/Target address, this mandates that the Fibre Channel Loop Id be very stable, and cannot be allowed to change if the system is sim- ply restarted. This might happen if soft addressing were used and the Fibre Channel Option found its previous address taken. Selecting a fixed address is a way to prevent the FCO Loop Id from changing if the system is restarted.
If the computer’s HBA uses the World Wide Port Name (WWPN) convention instead of the Loop Id to map to a SCSI Bus/Target/Lun address, the value of the Loop Id is no longer important. The WWPN is always unique and consistent under all conditions. In the future, all addressing will likely use the WWPN.
C••••••Fibre•Channel
•Device | SOFT |
Id Mode 0: | |
Loop Id 0: | nnn |
Topology 0: | LOOP |
Single Bay or one side of a Dual Bay Library
C••••••Fibre•Channel
•Device Left
•Device Right
L Id Mode 0: SOFT
L Loop Id 0: nnn
L Topology 0: LOOP
R Id Mode 0: SOFT
R Loop Id 0: nnn
R Topology 0: LOOP
Dual Bay Library with two FCO’s
The Configuration\Fibre Channel menu panel displays the SCSI device in- terface and configures the Fibre Channel Interface to host. The menu sets the Fibre Channel Option host topology. The “Topology” has two selections, LOOP and FABRIC. The LOOP selection configures the Fibre Channel Option for Arbitrated Loop
FCO Type A Installation | 501440 Rev. G |