Symptoms
When the host has two paths (A and B) to the disk array, the following steps are performed:
1.Remove the optical fiber of path A and reinsert it after the path status changes to Failed.
2.Read and write a LUN that has never been opened by any program. At this time, I/Os are delivered through path B which is in Enabled state.
When the optical fiber of path B is removed before the system updates the status of path A to Enabled, I/Os suspend.
Fault Diagnosis
The same problem occurs when the disk arrays from other vendors are used for tests.
In the path status check mechanism of AIX, the system periodically checks path statuses only when disks are in open state. In this scenario, the only path in Enabled state is removed, so no path is available for the system, causing I/O suspension.
Solution
Before staring services, ensure that physical connections are normal, and run the lspath command to check that normal paths are in Enabled state. If the status of any normal path is Failed, run the chpath -l hdiskX -s enable command to change the status to Enabled. If the status cannot be changed, check the physical connection.
The following provides an instance to explain specific steps:
1.Run the lspath command to check all the path statuses.
Note: hdisk5 has a Failed path.
2.Run the chpath -l hdisk5 -s enable commandto change the path status to Enabled.
3.Check the new path status.
