Some third-party ODMs use a different default value. Following that is a table showing the error count for the remote port that was in use when the error occurred. If using multiport adapters on the AIX host, split at least half the paths among separate physical adapters for optimum redundancy. This setting causes the path to be disabled. Disk Flash Servers Software Tape. When I ran the lsmpio and lspath commands on my system, I saw the following output:.
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The sequence for path selection within the list is customizable by modifying the path priority attribute on each path, which will then sort the list by the ascending path priority value.
This algorithm is available in the latest technology levels of AIX for some devices.
IBM AIX multipath I/O (MPIO) resiliency and problem determination
There are other possible configurations beyond what is described here that can be considered. This flag instructs chdev to attempt a dynamic update of the attribute value.
Ensure the appropriate settings are used on the subsystem see Subsystem notes above. View Public Profile for csorhand.
Monitor using the fcstat command. The enhancements in the new TL attempt to distinguish these induced errors from errors caused by the SAN issue to better identify the good paths and the problematic paths.
Best practice is to make the queue depth the same in both the server and client partition.
When I ran the lsmpio and lspath commands on my system, I saw the following output:. Following that is a table showing the error count qix the remote port that was in use when the error occurred.
AIX Recommended Settings – Pure1 Support Portal
When the SAN administrator specifies the -e flag, the lsmpio command output includes error counts for the local adapters and for the remote ports. So, it may continue to attempt to use the path that contains the failing component. In order to upgrade to the latest version of the ODM you will need to first remove the old one. Read The Current Issue: Stephan Linux 0 The general recommendation for the number of paths to configure in an MPIO environment is 4 to 8 per LUN, with 16 paths being recommended as the maximum, to be used only in specialized situations.
It is important to note that MPIO does support many more paths than 8 or 16, but from a design and functional mpioo, four to eight paths have been proven to be the most effective. For example, if the fiber connected to a particular AIX FC port is pulled out, all currently mpii paths originating at that port move to the Failed state.
It is completely possible to have full redundancy with four paths per LUN using dual fabrics. Installing any of the Hitachi ODM updates requires a reboot. Likewise, the host MPIO software may have difficulty in identifying the source component causing failures. To check the priority for each path, use the lspath command as follows: 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 ].
The new AIX technology levels added the -e flag for errors to the lsmpio command, to be used with the -a and -r flags. The default value for all devices is nonactive, and there is little reason to change this value unless business or application requirements dictate otherwise.
AIX Configuration Best Practice
It is not a driver. This can lead to much quicker recovery from a command time out and also much quicker detection of situations where all paths to a device have failed. Single path reserve, failover only Can be modified to: The lspath command or in newer technology levels, the lsmpio command can be used to determine the MPIO paths that are associated with specific SAN ports. To compound the issue, some error recovery actions may cause errors to occur on paths that are actually healthy.
For instance, the —S flag provides some interesting statistics and counters for hdisk devices.
Multipathing in AIX | Unix Linux Forums | AIX
Keep in mind that you will need to manually make this change anytime you overwrite the ODM i. A device that has multiple controllers can designate one controller as the active or preferred controller. The lsmpio command in older technology levels of AIX supports these two flags. Running the lsmpio -az command resets all of the above counters to zero.
This is accomplished by using multiple FC ports on both, the computer and the storage device.