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An Application Server and a Storage System in the Same Zone on an OceanStor SNS2120 Fail to Communicate with Each Other

Publication Date:  2018-08-28 Views:  185 Downloads:  0
Issue Description
An application server and a storage system are added to the same zone on an OceanStor SNS2120. However, the initiator that corresponds to the application server cannot be found on the storage system.
Alarm Information
OceanStor SNS2120 does not report any alarm.
Handling Process
1. Verify that the zone configuration is correct.
2. Verify that the optical fiber indicators are green.
3. Reseat the optical fibers. The problem persists.
4. Check ports on OceanStor SNS2120. It is found that I/O Stream Guard of some ports in the zone is set to Enable. When I/O Stream Guard of a port is set to Enable, the port will not receive registered state change notification (RSCN) from other ports whose I/O Stream Guard is also Enable. In this case, the zone configuration does not take effect, affecting communication.
Root Cause
I/O Stream Guard is a parameter of Fibre Channel ports on OceanStor SNS2120. Its possible values are Enable, Disable, and Auto. The default value is Auto (Disable).
If I/O Stream Guard for a port is set to Enable, the port will not receive RSCN sent from an external device, indicating that the external device is connected to or disconnected from the port (for example, when the external device is restarted). As a result, the status of the external device cannot be detected.
For an OceanStor SNS2120 whose firmware version is 8.0.x.x, I/O Stream Guard of ports will change from Auto (Disable) to Auto (Enable) if the following two conditions are met:
● The storage system uses QLogic HBAs.
● NPIV is enabled for the HBAs.
If the storage system uses the QLogic HBA as a target, the application server (as the initiator) and the target may simultaneously suppress RSCN, so that the application server cannot sense whether the target exists. As a result, the storage system and application server fail to detect each other, and no connection can be established between them.
Solution
Set I/O Stream Guard of the Fibre Channel ports on the switch to Disable, and power cycle the switch.

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