If the error count is zero, then the problem is likely resolved. For instance, the —S flag provides some interesting statistics and counters for hdisk devices. Subscribe me to comment notifications. 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. Thus the issue must be within the SAN fabric. This flag instructs chdev to attempt a dynamic update of the attribute value.
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The optimal configuration for a device having four paths on AIX is to use four physical paths to ,ultipath storage subsystem with a 1: All these types of errors may allow some FC packets to be transmitted correctly on the path, while other packets on that same path experience errors, causing a connection to partially work.
IBM AIX multipath I/O (MPIO) resiliency and problem determination
This gives an indication if the errors are still occurring or if perhaps there was a temporary issue that has not happened recently.
IBM AIX MPIO: Best practices and considerations
This also indicates a possible problem with the local FC adapter. I encourage you to read the documentation for this command on the AIX Information Center to learn more. Also, note that two different storage device ports have errors indicating that the issue is not associated with a single port on the storage device.
Note that the lsmpio command depends on support from the PCM.
This illustration shows the interaction between the different components that make up the MPIO solution. Storage Multipathing In Solaris 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 mulhipath AIX and four ports on the storage device. A path-control module PCM provides the path management functions.
Further problem determination requires knowledge of the SAN fabric topology. If scheduled maintenance is planned for a SAN or for a storage device, it is best to identify the disk paths that will be impacted by that maintenance and use the rmpath command to manually disable those paths before starting the maintenance.
The remaining sections of this article explain these improvements.
AIX Recommended Settings
The new improvements, include the following items:. The default value for all devices is nonactive, and there is little reason to change this value unless business or application requirements dictate otherwise.
The fileset allows your Jultipath box to correctly identify the disks as Hitachi disks. 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 mulyipath [the inter-switch link ISL ]. Configure 4 or 8 multpiath per disk, or up to 16 paths for rare situations.
For instance, the —S flag provides some interesting statistics and counters for hdisk devices. For example, perhaps the optical source on an FC port is becoming weak, a connection between the fiber and the port of an FC switch is not secure, or some device on a SAN fabric is malfunctioning in a way that is flooding that SAN fabric with extraneous traffic.
Note that the error count multtipath occurs only on one particular remote port. This output shows the current link state, multipzth then a count of errors that occurred on the adapter. For disks, this meant that the disk must be closed for example, volume group varied off in order to change attributes. Find all posts by h foorsa. With this flag, the attribute value can be changed without closing the disk and the change takes effect immediately.
Other PCMs might not implement this grace period.
The PCM KE depends on device configuration to detect paths and communicate that information to the device driver. 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. How to find out wheather multipathing is configured in AIX????? This flag instructs chdev to attempt a dynamic update of the attribute value.