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timeout_policy the new PCM attribute

Straight from IBM AIX Support:

The new PCM attribute for default AIX PCM, called timeout_policy.

http://www-01.ibm.com/support/docview.wss?uid=isg1IZ96396

timeout_policy adjusts the behavior of the PCM (Path Control Module) related to command timeouts, and transport errors. Setting timeout_policy to either fail_path or disable_path may decrease performance degradation when a MPIO device encounters intermittent SAN fabric issues on some, but not all the paths to the device.

retry_path = First occurrence of command timeout on path will not cause immediate path failure. If a path that failed due to transport issues is recovered by a health check, then that path may be used immediately.

fail_path = Path will be failed on first occurrence of a command timeout (assuming it is not the last path in the path group). If a path that failed due to transport issues recovers, the path will not be used for read/write I/O until a period of time has expired with no failures on that path. Enabling this feature may add a delay before read/write I/O is routed to paths that have just recovered from a transport error.

disable_path = Path will be failed on first occurrence of a command timeout (assuming it is not the last path in the path group). If a path that failed due to transport issues recovers, the path will not be used for read/write I/O until a period of time has expired with no failures on that path. If this path continues to experience multiple command timeouts during a period of time, then it may be disabled. Disabled paths remain disabled (and not usable), until a user specifically runs the chpath command to enable the disabled path (or the affected disk is reconfigured or system rebooted). This option is not recommended for most users, since it may require manual intervention to recover paths. Refer to chpath and lspath man pages for more details regarding uses of these commands.

Posted in Real life AIX.

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2 Responses

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  1. Sebastian says

    Hi, is this a IBM Storage only option? I can’t find this setting at our HDS LUNs.
    Cheers Sebastian

  2. MarkD:-) says

    Yes, this is for the SDDPCM diver from IBM not for HDS



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