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A LUN Fails to Be Created Because the LUN Is Suspended

Publication Date:  2013-05-30 Views:  121 Downloads:  1
Issue Description
When a LUN is being created, the ISM prompts "Cannot perform this operation currently because the system is busy."

Product models involved: S5500T/S5600T/S5800T/S6800T
Product scope involved: T series
Versions involved: all
Scenarios involved:
  •  The LUN is simultaneously accessed by multiple hosts (for example, in an active-standby cluster). Each host has two paths that are respectively connected controller A and controller B.
  •  One path of a host is down.
Alarm Information

None

Handling Process
Diagnosis Method:
1. Check the path disconnection logs. See [Cause].
2. Check the logs about the switchover of the owning controller of the LUN. See [Cause].

Solution:
Troubleshoot the path disconnection.

Check After Rectification:
There are no logs about the switchover of the owning controller of the LUN. The LUN can be successfully created.
Root Cause

1. The following log about the LUN creation failure is displayed in Message:

According to the log, the LUN creation failure is that the lock of the LUN cannot be obtained.

2. The previous logs show that the owning controller of the LUN is being switched, so the lock of the LUN cannot be obtained.

3. The logs of controller A show that host 10000000c9a3f567 is trying to switch the owning controller of the LUN to controller A.

4. The logs of controller B show that host 10000000c9a3f40e is trying to switch the owning controller of the LUN to controller B.

The host in this case is running the AIX operating system and resides in a cluster. Other hosts in the cluster can also detect the LUN. Therefore, the ping-pong effect occurs. In a multiple-path cluster, if the failover function is enabled for the owning controller of a LUN, when one path belonging to the owning controller is down, the host automatically switches the owning controller to the other controller. If at the same time, the two paths of another host are normal, the host tries to switch back the owning controller. As a result, the two hosts repeatedly switch the owning controller of the LUN over and back.
There are many events about the path disconnection (the path belongs to port P1 on Fibre Channel interface module 2 on controller A). This symptom meets the ping-pong effect. After troubleshooting the network, the fault is rectified, and the LUN can be successfully created.

The path disconnection causes the hosts to repeatedly switch the owning controller of the LUN, and the lock of the LUN is obtained throughout the process. As a result, the LUN fails to be created. After the path is recovered, the fault is rectified.
 

Suggestions
None

END