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Verifying the DM-Multipath configuration

You can use the multipath command on the Linux host to view the DM-Multipath configuration. You can change the amount of configuration detail that is displayed by using the -v parameter.

Steps

  1. Enter the following command on the Linux host: multipath -v3 -d -ll
    Note: The -d (dry run) parameter prevents the command from updating the multipath maps.
  2. Verify that the multipathd is running by entering the following command:
    • On Red Hat Enterprise Linux 6 and 5 series:/etc/init.d/multipathd status
    • On Red Hat Enterprise Linux 7 series: systemctl status multipathd
    Note: To determine if multipathd is working correctly on your system, enter the multipathd show config command. This command displays the values currently being used for the multipath.conf file. You can then confirm that multipathd is using the values you specified.
  3. To view a list of the multipath devices, including which /dev/sdx devices are used, enter the following command: multipath -ll
    Example
    (FC) The output looks similar to the following for FC:
    # multipath -ll
    3360a98000486e5372635a44646a505643NETAPP,LUN
    [size=10G][features=1 queue_if_no_path][hwhandler=0]
    \_ round-robin 0 [prio=8][active]
     \_ 6:0:0:0 sda 8:0   [active][ready]
     \_ 7:0:1:0 sdg 8:96  [active][ready]
    \_ round-robin 0 [prio=2][enabled]
    \_ 6:0:1:0 sdc 8:32  [active][ready]
     \_ 7:0:0:0 sde 8:64  [active][ready]
    Example
    (FC and clustered Data ONTAP) If the storage system is running clustered Data ONTAP and using iSCSI, the output looks similar to the following:
    # multipath -ll
    360a98000486e2f66426f2f7a32745338 dm-0 NETAPP,LUN C-Mode
    size=1.0G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
    |-+- policy='round-robin 0' prio=50 status=active
    | |- 3:0:1:1 sdd 8:48 active ready running
    | |- 3:0:4:1 sdh 8:112 active ready running
    | |- 2:0:0:1 sdj 8:144 active ready running
    | `- 2:0:2:1 sdn 8:208 active ready running
    `-+- policy='round-robin 0' prio=10 status=enabled
    |- 3:0:0:1 sdb 8:16 active ready running
    |- 3:0:2:1 sdf 8:80 active ready running
    |- 2:0:1:1 sdl 8:176 active ready running
    `- 2:0:3:1 sdp 8:240 active ready running
    
    
    Example
    (FC on Red Hat Enterprise Linux 6, SUSE Linux Enterprise Server 11 SP1 or later) The output looks similar to the following when you have ALUA enabled and are using either Red Hat Enterprise Linux 6 or SUSE Linux Enterprise Server 11 with SP1 or later:
    # multipath -ll
    360a98000486e2f66426f2f7a32745338 dm-0 NETAPP,LUN
    size=1.0G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
    |-+- policy='round-robin 0' prio=50 status=active
    | |- 3:0:1:1 sdd 8:48  active ready running
    | |- 3:0:4:1 sdh 8:112 active ready running
    | |- 2:0:0:1 sdj 8:144 active ready running
    | `- 2:0:2:1 sdn 8:208 active ready running
    `-+- policy='round-robin 0' prio=10 status=enabled
      |- 3:0:0:1 sdb 8:16  active ready running
      |- 3:0:2:1 sdf 8:80  active ready running
      |- 2:0:1:1 sdl 8:176 active ready running
      `- 2:0:3:1 sdp 8:240 active ready running
    
    Example
    (FC on Red Hat Enterprise Virtualization Hypervisor 6.2) The output looks similar to the following when you have ALUA enabled and are using Red Hat Enterprise Virtualization Hypervisor 6.2:
    # multipath -ll
    360a98000316b5a776b3f2d7035505a6f dm-0 NETAPP,LUN
    size=60G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 alua' wp=rw
    |-+- policy='round-robin 0' prio=50 status=active
    | |- 4:0:0:0 sda 8:0   active ready running
    | `- 5:0:0:0 sdc 8:32  active ready running
    `-+- policy='round-robin 0' prio=10 status=enabled
      |- 4:0:1:0 sdb 8:16  active ready running
      `- 5:0:1:0 sdd 8:48  active ready running
    
    Example
    (iSCSI and clustered Data ONTAP) If the storage system is running clustered Data ONTAP and using iSCSI, the output looks similar to the following:
    # multipath -ll
    3600a09803246676c703f2d6c36506138 dm-0 NETAPP,LUN C-Mode
    size=25G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
    |-+- policy='round-robin 0' prio=50 status=active
    | `- 8:0:0:0  sdc 8:32 active ready running
    `-+- policy='round-robin 0' prio=10 status=enabled
      |- 9:0:0:0  sdd 8:48 active ready running
      |- 7:0:0:0  sdb 8:16 active ready running
      `- 10:0:0:0 sde 8:64 active ready running
    
    Example
    (iSCSI on Red Hat Enterprise Linux 6, SUSE Linux Enterprise Server 11 SP1 or later) The output looks similar to the following when you are using iSCSI with either Red Hat Enterprise Linux 6 or SUSE Linux Enterprise Server 11 with SP1 or later:
    # multipath -ll
    360a9800050334b50694a625563326f37 dm-3  NETAPP,LUN
    size=9.0G features='1 queue_if_no_path' hwhandler='0' wp=rw
    `-+- policy='round-robin 0' prio=2 status=active
      |- 4:0:0:1 sdc 8:32  active ready running
      `- 3:0:0:1 sdb 8:16  active ready running
    
  4. To check what DM-Multipath settings are currently in use on a Linux host, you must run the following commands:
    • RHEL6 hosts: multipathd show config
    • RHEL5 hosts: multipathd -k"show config
    • SLES11 hosts: multipathd show config

    You must refer to the output from the above commands to verify whether the NetApp recommended DM-Multipath settings are currently in use. For more details on these commands, refer to the man pages.

  5. To view the /dev/mapper devices, enter the following command:ls -l /dev/mapper/
    Example
    The following example shows the sample output of the ls -l dev/mapper command:
    total 0
    brw------- 1 root root 253, 1 Sep 20 17:09 360a98000486e5363693444646a2f656c
    brw------- 1 root root 253, 0 Sep 20 17:09 360a98000486e5372635a44646a505643
    lrwxrwxrwx 1 root root     16 Sep 12 10:16 control -> ../device-mapper