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Editing the DM-Multipath configuration file

For DM-Multipath to function properly, you must edit the /etc/multipath.conf configuration file.

Steps

  1. If the /etc/multipath.conf file exists, edit it to include the sections needed for your system.
  2. If you do not have the /etc/multipath.conf file, copy the sample configuration file for your operating system. The following sections provide sample configuration files for several versions of Red Hat Enterprise Linux and SUSE Linux Enterprise Server.
  3. After you have the file, you can specify which devices you want to exclude (blacklist).

    You should exclude all the devices that do not correspond to LUNs configured on the storage system that are mapped to your Linux host. That is, exclude those devices that are not displayed by the sanlun lun show command.

    Note: You must supply information that is specific to your system. Otherwise, you will encounter problems.

    The following steps explain what you need to do to exclude a device:

    1. In the blacklist section of the configuration file, enter the WWID of all non-NetApp SCSI devices installed on your host.
      You can get the WWID by running the scsi_id command on a device.
      Example
      For example, assume that /dev/sda is a local SCSI drive. To obtain the WWID on systems running Red Hat Enterprise Linux 7 or 6 series or SUSE Linux Enterprise Server 11, enter: /lib/udev/scsi_id -gud /dev/sda

      To obtain the WWID on systems running other Linux operating systems, enter: scsi_id -gus /block/sda

      In both cases, the output looks similar to the following: SIBM-ESXSMAW3073NC_FDAR9P66067W

      To exclude that device, enter SIBM-ESXSMAW3073NC_FDAR9P66067W in the blacklist section of the configuration file:

      blacklist
      {
        wwid IBM-ESXSMAW3073NC_FDAR9P66067W
        devnode "^hd[a-z]"
        devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
        devnode "^cciss.*"
      }
    2. Exclude other devices by using the devnode, such as: devnode "^hd[a-z]"devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"devnode "^cciss.*"
      Example
      On Red Hat Enterprise Linux 4 hosts, the blacklist section might appear as the following:
      devnode_blacklist 
      {
      devnode "^hd[a-z]"
      devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*" 
      devnode ^cciss.*"
      wwid SIBM-ESXSMAW3073NC_FDAR9P66067WJ
      }
  4. Make sure you use the correct settings based on whether you are using ALUA.
    If you are using ALUA, you must specify the ALUA callout program. If you are not using ALUA, you must specify the Data ONTAP callout program. The following table provides information on the values that you must supply.
    Note: If you are using clustered Data ONTAP, you must have ALUA enabled.
    If you are running... With ALUA, use the value Without ALUA, use the value
    SUSE Linux Enterprise Server 10 SP2 and later, SUSE Linux Enterprise Server 11 and later, or Red Hat Enterprise Linux 6.0 and later Set prio to: “alua” Set prio to: “ontap”
    Any other Red Hat Enterprise Linux operating system Set prio_callout to: /sbin/mpath_prio_alua Set prio_callout to: /sbin/mpath_prio_ontap
    SUSE Linux Enterprise Server 10 SP1 and SP2 ~ Set prio_callout to: /sbin/mpath_prio_ontap
    All supported Linux operating systems that support ALUA Set hardware_handler to: "1 alua" Set hardware_handler to: "0"
    Note: ALUA is supported in Red Hat Enterprise Linux 5 Update 1 or later, SUSE Linux Enterprise Server 10 SP2 or later, and SUSE Linux Enterprise Server 11 or later.
  5. Save the changes.