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IZ96396: TIMEOUT_POLICY ATTRIBUTE FOR AIX PCM APPLIES TO AIX 7100-00

A fix is available

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APAR status

  • Closed as program error.

Error description

  • When running MPIO device with round_robin algorithm, disk
    I/O throughput may be greatly affected by one or more paths
    failing then coming back online.
    

Local fix

Problem summary

  • When running MPIO device with round_robin algorithm, disk
    I/O throughput may be greatly affected by one or more paths
    failing then coming back online.
    

Problem conclusion

  • Add new PCM attribute for default AIX PCM, called
    timeout_policy.  timeout_policy set to "fail_path" will
    resolve many continuous performance degradation issues on
    MPIO devices connected via a path (or switch) going up and
    down.
    
    timeout_policy values are defined as follows:
    retry_path = Similar to existing PCM behavior, 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 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 for routing I/O to paths that have just
    recovered.
    
    disable_path = Path will be failed on 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 command timeouts during a period of time, then
    path may be disabled.  Disable paths remain disabled (and not
    used), until user specifically runs chpath command to enable
    the disable path (or disk is reconfigured or system rebooted).
    This option is not recommended for most users, since it may
    require some intervention to recover paths.
    

Temporary fix

Comments

  • 6100-06 - use AIX APAR IZ96302
    7100-00 - use AIX APAR IZ96396
    

APAR Information

  • APAR number

    IZ96396

  • Reported component name

    AIX V7.1

  • Reported component ID

    5765H4000

  • Reported release

    710

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Submitted date

    2011-03-09

  • Closed date

    2011-03-09

  • Last modified date

    2012-05-18

  • APAR is sysrouted FROM one or more of the following:

    IZ96302

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    AIX V7.1

  • Fixed component ID

    5765H4000

Applicable component levels

  • R710 PSY U833011

       UP11/05/12 I 1000

PTF to Fileset Mapping



Document information

More support for: AIX Enterprise Edition

Software version: 710

Operating system(s): AIX

Reference #: IZ96396

Modified date: 18 May 2012