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Disabling MPIO

The Multiple Path I/O (MPIO) feature was introduced in AIX 5.2 to manage disks and LUNs with multiple paths. By default, MPIO is enabled on all disks and LUNs that have this capability, which prevents DMP or other third-party multipathing drivers (such as EMC PowerPath) from managing the paths to such devices.

To allow DMP or a third-party multipathing driver to manage multipathing instead of MPIO, you must install suitable Object Data Manager (ODM) definitions for the devices on the host. Without these ODM definitions, MPIO consolidates the paths, and DMP can only see a single path to a given device.

There are several reasons why you might want to configure DMP to manage multipathing instead of MPIO:

Contact the array vendor to obtain ODM definitions for the array type and the version of AIX on your system. The ODM definition should permit either DMP or the array vendor's multipathing driver to discover the devices in the supported array.

Having obtained the packages that contain the new ODM definitions, perform the following steps to configure DMP or an array vendor's multipathing driver in place of MPIO:

  1. Unmount any file systems and stop all applications such as databases that are configured on VxVM volumes.
  2. Stop all I/O to the VxVM volumes by entering the following command for each disk group:

    # vxvol -g diskgroup stopall

  3. Use the vxprint command to verify that no volumes remain open:

    # vxprint -Aht -e v_open

  4. Deport each disk group in turn:

    # vxdg deport diskgroup

  5. Use the following command to remove each hdisk device that MPIO has configured to the arrays:

    # rmdev -dl hdisk_device

    Alternatively, use the smitty rmdev command.

  6. To remove the existing MPIO packages, run the following command:

    # installp -u MPIO_package ...

    Alternatively, use the smitty installp command.

  7. Use the installp command to install the replacement ODM packages:

    # installp ODM_package ...

  8. Reboot the system so that the new ODM definitions are used to perform device discovery.
  9. Use the vxdmpadm command to check that DMP now has access to all the paths to the devices. The following command displays a list of HBA controllers that are configured on a system:

    # vxdmpadm listctlr all

    The next command displays information about all the paths that are connected to a particular HBA controller (for example, fscsi2):

    # vxdmpadm getsubpaths ctlr=controller