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Tape Libraries and Drives
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Cannot detect Tape Library after changing SAN switch port for host connectivity

Chuen Woon Liang
Occasional Contributor

Cannot detect Tape Library after changing SAN switch port for host connectivity

Hi All,

I am facing a strange problem, any comments and suggestions are most welcome.

Below are the summary of the connectivity
1) 2 x Existing SAN switch (let name it SW01 & SW02) both form two seperate fabrics
2) 2 hosts (Windows 2003 cluster) are connecting to SW1 & SW2 respectivitely
3) ESL with 3 x NSR are connecting to SW1
4) Persistent Binding are configured in W2003 hosts for tape devices
5) Zoning are configured in SW1 & SW2 for storage access and ESL Library access
6) Old EMA storage is connected to SW1 & SW2
7) Everything work fine before changes

Below are the changes
Data migration
1) Ading 2 x SAN switches (let name it SW3 & SW4)
2) SW3 is cascaded to SW1 and SW4 is cascaded to SW2
3) EVA is connected to SW3 & SW4
4) New zone being created for hosts to access EVA
5) Data migration being performed for for cluster from EMA to EVA
6) Everything work fine after data migration and hosts can still access the ESL Library

Change the host connectivity to SW3 & SW4, (HBAs remain same on hosts)
7) New zone being created to allow hosts port in SW3 to access the ESL library
8) Unplug the existing FC cables and insert the FC cables which connect to SW3 & SW4
9) Cluster running fine and all the disks are accessible
10) However the hosts (W2003) no longer able to detect the ESL Library anymore
11) Failback the existing FC cables, the hosts can detect the ESL Library

1) Zoning are configured correctly to allow host port in SW3 to access ESL Library
2) No changes to Persistent binding and NSR configuration on ESL
3) HBAs which original connected to SW1 are connected to SW3

1) Why after the cables swapped the hosts no longer able to detect the ESL anymore (zoning is confirmed in place) and the connectivity to EVA is okay ?
2) To my knowledge, the persistent binding is based on WWN and NSR host mapping also based on WWN, we should not need to perform any changes in persistent binding and NSR as the HBA cards is not changed (still the same WWN for HBAs and same WWN for NSR deivices)
3) Any of Persistent binding and NSR host mapping will be impacted by FCID (when host port connected to SW3 will trigger the FCID changes)?
4) What is "Host ID" in NSR host mapping configuration ?

Any answers and suggestions are welcome.


Chuen Woon Liang
Occasional Contributor

Re: Cannot detect Tape Library after changing SAN switch port for host connectivity

The problem has been resolved.

The problem was due to the "Host ID" in NSR host mapping. The "Host ID" is the FCID of the SAN switch port, patching the server to any SAN switch port cause the mismatch of "Host ID" in NSR and FCID.

After deleting the old host entry with "old Host ID", all the devices behind the NSR can be seen.