Recent technology levels of AIX also make use of asynchronous events from the Fibre Channel FC device drivers to manipulate path states. So redundant path here is used only as a failover. The default value for all devices is nonactive, and there is little reason to change this value unless business or application requirements dictate otherwise. So nonzero counts, especially large nonzero counts, are more interesting than a small or zero error count. The previous recommendation from AIX development stands in those cases:

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It is completely possible to have full redundancy with four paths per LUN using dual fabrics. However, certain switch or port failures might affect an entire SAN, thus impacting all four paths. If a component has a solid, permanent failure, the failure can be easily detected either by the MPIO software in AIX or by mpoi firmware in the storage device.

If a disk is not open and in use as is the case, for instance, when its volume group is varied off, no path health checks will take place down any path for that disk. However, the cost of setting a lower health check interval far outweighs the benefits.

IBM AIX multipath I/O (MPIO) resiliency and problem determination

The AIX system error report shows errors for a particular FC port and shows disk path failures for paths using that particular port. Following that is mppio table showing the error count for the remote port that was in use when the error occurred.


This article discussed those improvements and demonstrated how a SAN administrator can use the new features of the lsmpio command during problem determination. Typically, users configure the SAN fabric with more than one path between the computer and the storage device.

Sign in or register to add and subscribe to comments. This algorithm is available in the latest technology levels of AIX for some devices.

This is just an example.

IBM AIX MPIO: Best practices and considerations

But something associated with that adapter is causing errors. The AIX lsmpio command shows many paths in the Failed state for one particular port. After the two 8-path hdisks are configured as a single HyperSwap enabled hdisk, it will have 16 paths. So redundant path here is used only as a failover. This setting causes the path to be disabled.

This gives an indication if the errors are still occurring or if perhaps there was a temporary issue that has not happened recently.

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This flag instructs chdev to attempt a dynamic update of the attribute value. To compound the issue, some error recovery actions may cause errors to occur on paths that are igm healthy.

New lsmpio Command Provides Better View of MPIO

View image at full size. The lsmpio command implements the -a and -r flags to show the local and remote FC ports used by the disks.

Thus if a single adapter fails, the other adapter provides access to the storage device. X We use cookies to optimize your visit to our website. Thus the jbm must be within the SAN fabric.


IBM AIX multipath I/O (MPIO) resiliency and problem determination

That includes paths with a state of failed. Those path states make it kbm that there is a failure associated with the link for that particular port, and therefore, it is easy for the user to determine the source of the ib. You are commenting using your Facebook account.

A disabled path is only recovered by manual user intervention using the chpath command to re-enable the path. This output shows the current link state, and then a count of errors that occurred on the adapter. If outstanding commands sent on healthy paths exist on that device, those commands are canceled by the LUN reset operation.

The AIX node and the storage device each have two ports connected to each of the two SAN fabrics, using a jbm of four ports on AIX and four ports on the storage device. If using two switches, there is no single point of failure. This may be useful for determining if a problem is still occurring or if a problem has been resolved.