Sorry, your blog cannot share posts by email. This setting causes AIX to fail the path after a single command timeout, assuming that the device has at least one other path that is not in the failed state. The health checker never probes paths that are in a Disabled or Missing state. 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 ]. Disk Flash Servers Software Tape.

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Optimal performance in a failed path scenario is to ensure that the ordered path list alternate paths between separate fabrics. Connecting to one or more ports on each of the controllers protects against the failure of an entire storage device controller.

Enterprises must occasionally restructure their infrastructure to meet new IT requirements and handle scheduled outages such as scheduled system maintenance. Also notice kpio the errors occurred across all of the remote ports accessed by fscsi1. Also, note that the lsmpio command accepts a -z flag to zero out the error counters.

Likewise, the host MPIO software may have difficulty in identifying the source component causing failures.

You are commenting using your Twitter account. If outstanding commands sent on healthy paths exist on that device, those commands are canceled by the Mpjo reset operation. 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.

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The AIX node and the storage device each have two ports connected to each of the two SAN fabrics, using a total of four ports on AIX and four ports on the storage device. AIX MPIO stops using any disabled or Defined paths, and therefore, no error detection or recovery will be done as a result of the scheduled maintenance.

IBM AIX MPIO: Best practices and considerations

Ibn find out more, including how to control cookies, see here: For instance, the —S flag provides some interesting statistics and counters for hdisk devices. Subscribe me to comment notifications. 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.

The AIX lsmpio command shows many paths in the Failed state for one particular port. A path that is failed due to timeout policy can later be recovered by the AIX health check commands. Note that the lsmpio command depends on support from the PCM.

You are commenting using your WordPress. This system was connected to an XIV storage system. Likewise, using multiple FC ports on the storage device protects against the failure of a single port. This output shows the current link state, and then a count of errors that occurred on the adapter. Changes the characteristics of the device while allowing the device ib, remain in the Available state. Also notice that the output categorizes the error count into different time ranges.

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Using multiple paths might provide obm bandwidth, but more importantly multiple paths provide redundancy to protect against failures of SAN fabric components. Gary Domrow Published on February 19, Notify me of new comments via email. You can leave a responseor trackback from your own site. There are other possible configurations beyond what igm described here that can be considered. For example, you can quickly determine if any errors have been recorded for a device. However this error detection and recovery might take some time, and that delay might impact applications.

IBM AIX MPIO: Best practices and considerations

So nonzero counts, especially large nonzero counts, are more interesting than a small or zero error count. System reliability and availability are increased by a careful consideration of the user-modifiable options in each system configuration.

I verified this on my lab system running AIX 6. The disk attributes described in the following sections can be displayed by using the lsattr command, and can be changed with the chdev command.