Please take note of the following important information in the Technote S I mentioned earlier: Businesses that need to configure more than eight paths per LUN need to carefully consider the following details:. One or more of the selected filesets will cause a bosboot to be performed. 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. Last 10 Minu tes: 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 bosboot command will rebuild the boot image.

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However, the hdisk that is booted from cannot be closed and hence, the host attachment script for SDD cannot be removed. The active rootvg of the SAN boot device is in Open state and hence, the device cannot be removed by the rmdev command.

This ensures that the AIX host does not go into extended error recovery for a scheduled maintenance activity. Comments Sign in or register to add and subscribe to comments. Please take note of the following important information in ibbm Technote S I mentioned earlier: Any modification made to the queue depth prior to removal will need to be reapplied. The values of the attributes of the disks are not preserved during this aiz.

This setting causes the path to be disabled. This flag instructs chdev to attempt a dynamic update of the attribute value.


As a result it may. One possible eight-path configuration that provides full redundancy uses two distinct SAN fabrics. The only case for more than eight paths is for specialized ibn devices that configure a cluster of controllers, or for devices using Peer-to-Peer Remote Copy PPRC.

Sign in or register to add and subscribe to comments. It might be tempting to think that a smaller health check interval is preferable as it might lead to faster detection or recovery of failed paths.

This represents the legacy behavior, where a command may be retried on the same path that just experienced a command timeout. The bosboot command will rebuild the boot image.

Subsystem Device Driver Path Control Module (SDDPCM) for IBM AIX

Similar Ideas Using an Ideation Bl Watson Product Search Search. However, the host attachment script cannot be removed because of the active rootvg of the open hdisk. For disks, this meant that the disk must be closed for example, volume group varied off in order to change attributes. AIX Live Update with Configure 4 or 8 paths per disk, or up to 16 paths for rare situations.

With this flag, the attribute value can be changed without closing the disk and the change takes effect immediately. When disabling multiple paths for multiple LUNs, rmpath is simpler than chpathas it does not have to be run on a per-disk basis. 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.


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. 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. After the maintenance is complete, the paths can be re-enabled with cfgmgr.

It is completely possible to have full redundancy with four paths per LUN using dual fabrics. Type or select values in entry fields. However this error detection and recovery might take some time, and that delay might impact applications.

Subscribe me to comment notifications. A path that is failed due to timeout policy can later be recovered by the AIX health check commands.

One “Path Control Module” to Rule Them All! (Chris’s AIX Blog)

If multiple disks were to encounter similar issues at the same time, the consequences for applications might be severe. This can lead to much quicker recovery from a command time out and also much quicker detection of situations six all paths to a device have failed.

None of the above, continue with my search. System reliability and availability are increased by a careful consideration of the user-modifiable options in each system configuration.