Thus, algorithms that use all available paths might only use a subset of those paths at one time for such devices. Some third-party ODMs use a different default value. This illustration shows the interaction between the different components that make up the MPIO solution. This flag instructs chdev to attempt a dynamic update of the attribute value. Assigning a vertual IP and doing IP multipathing The following sections discuss the output of various samples of the lsmpio command. T he queue depth setting in the ODM should be treated as a possible starting point, and may need to be adjusted based on host environment variables.

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Paths in those two states must be recovered manually with chpath for Disabled paths or with cfgmgr for Missing paths.

However, as noted above, going beyond eight paths can be more problematic than helpful, and should be carefully considered. It may be a problem with that adapter, the fiber connected to the adapter, or perhaps the port on the FC switch that the fiber is connected to.

If scheduled maintenance is planned for a SAN or for a storage device, it is best to identify the mulyipath paths that will be impacted by that maintenance and use the rmpath command to manually disable those paths before starting the maintenance. The following section provides technical details regarding this best practice recommendation.

Miltipath a Forum Member? This ensures that the AIX host does not go into extended error recovery for a scheduled maintenance activity.

Likewise, using multiple FC ports on the storage device protects against the failure of a single port. The new improvements, include the following items:. I think IBM storage brings its own multipath software too not sure – I seem to end up always in EMC companies If your storage is presented via vscsi from the vio servers, than AIX will use MPIO pretty much by default but you will have to set up the failover and path settings like queuedepth and priority The time now is If the disk could not be closed, such as the disks containing rootvg, then the user had to include the -P flag in the chdev command to write the attribute change to ODM and then restart AIX in order for the attribute to take effect.


One possible eight-path configuration that provides full redundancy uses two distinct SAN fabrics.

With this flag, the attribute value can be changed without closing akx disk and the change takes effect immediately.

Stephan Linux 0 Configure 4 or 8 paths per disk, or up to 16 paths for rare situations. Pure Storage supports a maximum read and write transfer size of 4MB.

Multiple Path I/O

Similar to the first case, this indicates an issue with one particular FC port, but this time the problematic port is on the storage device. When disabling multiple paths for multiple LUNs, rmpath is simpler than chpathas it does not have to be run on a per-disk basis. Thus, algorithms that use all available paths might only use a subset of those paths at one time for such devices.

As a result, the default values for the attributes are appropriate for most situations. A device that has multiple controllers can designate one controller as the active or preferred controller. For disks, this meant that the disk must be closed for example, volume group varied off in order to change attributes.

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

That includes paths with a state of failed. If using multiport adapters on the AIX host, split at least half the paths among separate physical adapters for optimum redundancy.


In fact, an excessive number of paths in an MPIO configuration can actually contribute to system and application performance degradation in the event of SAN, storage, or Fibre Channel fabric issues or failures.

This flag instructs chdev to multipaath a dynamic update of the attribute value. It is much more likely to be a good idea to increase the health check interval than to decrease it.

The AIX lsmpio command shows many paths in the Failed state for one particular port.

IBM Systems Magazine – New lsmpio Command Provides Better View of MPIO | AIX | IBM Systems Magazine

View image at full size. In this case, I had somewhat artificially plugged two of the storage device ports into a second switch, and inserted the jammer in the link between the switches [the inter-switch link ISL multkpath. Gary Domrow Published on February multipafh, Looking at the system error report, there may be TEMP disk errors, indicating that certain Small Computer System Interface SCSI commands failed on their first attempt, but were successful when retried, perhaps down a different path.

Note that there could be cases where the error total listed directly under the adapter exceed the sum of the errors on the remote ports under the adapter, as some errors may not be associated with a particular remote port.

The attributes six be displayed or changed using the SMIT, or commands in particular, the lsattr and the chdev commands.