Product and version:
S5500T V100R001 V100R002
S5600T V100R001 V100R002
S5800T V100R001 V100R002
S6800T V100R001 V100R002
The operating system of the application server: SUSE Linux Enterprise Server 11（x86_64）
HBA card is: QLogic HBA
Connect the double paths directly (A controller and B controller) for networking, the host and storage device have created a connection normally and map LUN (the LUN belongs to the A controller) to the host successfully. The host execute the I/O read and write operation for the LUN, in this process, plug out the fiber cable from the A controller, switch the I/O path to the B controller, plug in the fiber again, the I/O path can’t failback from the B controller to the A controller.
Step 1. Plug the fiber cable again, execute the “hot_add” to scan the LUN on the host, then check if there is new path created via “upTools –S”.
YES => Completed
NO => Step2
Step 2. Check whether the fiber cable is well or not. If there isn’t any problem of the fiber cable, try plugging it into another port or add a fiber connection; if the fiber cable has problem, please replace it. Execute the “hot_add” to scan the LUN on the host, then execute the “upTools –S” to check if there is new path created.
YES => Completed
NO => Step 3
Steps 3.We recommend you transfer the services to another host, and then restart the host, after the system has restored, then transfer the corresponding services back.
Background: In the process of host executing the I/O read and write operation for the LUN, plug out the fiber cable from the A controller, switch the I/O path to the B controller.
After plugging in the fiber, view the current path information via the “upTools –S”, we find there isn’t path in the A controller. As the figure 1 displayed:
Figure 1. The path information
Check the logs (/var/log/messages), there isn’t physical information reporting, the system can’t create the physical path. There will be the following information if a device is reported, as the figure 2 displayed.
Figure 2. Logs information
Therefore, the I/O path can’t failback from the B controller to the A controller. According to the above condition, we conclude that it’s the driver’s fault of the HBA card which caused there hasn’t reported the physical device.
In the condition of FC physical link network, try to reduce the plugging of the fiber cable as far as possible.