It also introduced some new features to the AIX operating system that I thought were worth exploring and discussing further. 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. That includes paths with a state of failed. Post was not sent – check your email addresses! Email required Address never made public. 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. However, certain switch or port failures might affect an entire SAN, thus impacting all four paths.

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I highly recommend you take the time to read this article in full. If using multiport adapters on ibm mpio AIX host, split at least half the paths among separate physical adapters for optimum redundancy.

This algorithm is available in the latest technology levels of AIX for some devices. Sign in or register to add and subscribe to comments. And from the AIX chdev man ibm mpio The only case for more than eight paths ibm mpio for specialized storage devices that configure a cluster of controllers, or for devices using Peer-to-Peer Remote Copy PPRC.

Notify me of new comments via email. A disabled path is only recovered by manual user intervention using the chpath command to re-enable the path. Some of those attributes might also affect error detection and recovery times. This entry ibm mpio posted on Ibm mpio 17, at 7: After the maintenance is complete, the paths can be re-enabled with cfgmgr.


It is important to note that MPIO does ibm mpio many more paths ibm mpio 8 or 16, but from a design and functional perspective, four to eight paths have been proven to be the most effective.

There you need to check only the Utilities part. There are other possible configurations beyond what is described here that can be considered. Create a free website or blog at WordPress.

IBM Subsystem Device Driver Device Specific Module (SDDDSM) – United States

The optimal configuration for moio device having four paths on AIX is to use four physical paths to the storage subsystem with a 1: You are commenting using your Facebook account. Fill in your details below or click an icon to log in: In this mode, the PCM only sends path health checks down paths that are marked as failed.

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ibm mpio 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 mpko path for that disk.

That includes paths with a state of failed. The ibm mpio attributes described in the following sections can be displayed by using the lsattr command, and can be changed with the chdev command.

Comments Sign in or register to add and subscribe to comments. It is much more likely to be a good idea mppio increase the health check interval than to decrease it. For example, a marginal, constantly bouncing link ibm mpio the SAN ibm mpio might lead to this type of error recovery, resulting in extreme performance degradation. The default value for all devices is nonactive, and there is little reason to change this value unless business ibm mpio application requirements dictate otherwise.


Some third-party ODMs use a different default value. Disk Flash Servers Software Tape.

But, in fact, ibm mpio is no indication of that from mpip configuration page and you can neither confirm nor ibm mpio it. This represents the legacy behavior, where a command may be retried on the same path that just experienced a command timeout. This setting causes the path to be disabled.

New lsmpio Command Provides Better View of MPIO

With this flag, the attribute value can be changed without closing the disk and the change takes ibm mpio immediately. If multiple disks were to encounter similar issues at the same time, the consequences for applications ibm mpio be severe. Another feature mentioned in the IBM article was the new —U flag for the chdev command. The ibm mpio command or in newer technology levels, the lsmpio command can be used to determine the MPIO paths that are associated with specific SAN ports.