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Loops, ports and switches

Hello Marc,

I enjoyed reading "Building Storage Area Networks". It provided me with pictures I was trying to visualize in my head. Not having worked on a Enterprise level SAN, the blueprints were a nice addition to the technical information you provided.

When working with a SilkWorm 2800, with Solaris N-Ports (JNI), Native Fibre Channel STK9840 tape drives (Public Loop Ports) and (1) Crossroads bridge (N-Port), I see the bridge participating in what seems to be administrative duties when changing the status of other ports on the switch. For instance, when I disable a port on the switch supporting one of the tape drives, I see the port (Port 1) that the bridge is plugged in to participating in the LOGO procedures. And when I re-enable the port, I see the bridge port participating in the LOGI procedures.

Here are my questions:

Why is Port 1 participating in the LIP's/Fabric Login or Logout of other ports on the switch? And isn't each port on the switch supporting the Public Loop Tape Drive a FL-Port? Meaning, would each FL-Port serve as Loop Master for each tape drive? Or, is the port with the lowest value AL_PA considered the Loop Master?

Thank you for your answer.

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I'm sorry, but the description of the SAN in the question isn't clear enough to me. What is the relationship between the bridge and the tape drive? What is connected to the bridge? What is connected through loops? How many loops are there? Is there any loop bridging going on in the switch? How many devices are connected to the switch through F ports and how many through FL-ports?

Marc Farley

This was first published in April 2001

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