Check here to start a new keyword search. Comments Sign in or register to add and subscribe to comments. Please contact us for new versions of the scripts. One possible eight-path configuration that provides full redundancy uses two distinct SAN fabrics. If using multiport adapters on the AIX host, split at least half the paths among separate physical adapters for optimum redundancy.

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If multiple disks were to encounter similar issues at the same time, the consequences for applications might be severe. There are several reasons for this.

If this is not done, other nodes in the cluster will lose access to the shared disks until the reservation policy is changed.

Thus, algorithms that use all available paths might only use a subset of those paths at one time for such devices. This makes AIX less dependent on the health check commands to detect path failures or to recover paths when using Fibre Channel.

IBM Subsystem Device Driver for AIX – United States

This is just an example. After the OS upgrade completes, the correct SDD version must be installed and the host attachment script must be reinstalled. However, the host attachment script cannot be removed because of the active rootvg of the open hdisk.

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Please contact us for new versions of the scripts. This setting causes the path to be disabled. Carefully consider the impacts of extra, unnecessary redundancy before using more paths.

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Cause The active rootvg of the SAN boot device is in Open state and hence, the device cannot be removed by the rmdev command. 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.


After the two 8-path hdisks are configured as a single HyperSwap enabled hdisk, it will have 16 paths. One possible eight-path configuration that provides full redundancy uses two distinct SAN fabrics. United States English English. Find the duplicate idea: The -l option shows a list of all options available the columns show the device family, the driver currently used by that family, and the different options available.

For disks, this meant that the disk must be closed for example, volume group varied off in order to change attributes. It is completely possible to have full redundancy with four paths per LUN using dual fabrics.

This ensures that the AIX host does not go into extended error recovery for a scheduled maintenance activity. The previous recommendation from AIX development stands in those cases: 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.

In an MPIO configuration, more is not necessarily better. For the newest technology levels of AIX sed the time of publishing this articlesome disk attributes on some devices support the -U flag on the chdev command.

The chdev command may be used to change the reservation policy, as follows, shown for hdisk Some of those attributes might also affect error detection and recovery times. If the disk could not be closed, such as the disks containing rootvg, then sdc 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.


Customers have requested we provide instructions to perform this upgrade process within this technote. System reliability and availability are increased by a careful consideration of the user-modifiable options in each system configuration.

IBM Subsystem Device Driver Path Control Module (SDDPCM) – United States

The path priority values are sed by this sdr. As a result, the default values for the attributes are appropriate for most situations. It is important to note that MPIO does support many more paths than 8 or 16, but from a design and functional perspective, four to eight paths have been proven to be the most effective. For most attributes and most levels of AIX, attributes could historically only be changed on devices that were not in use.

Document information More support for: 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.