Verifying the DM-Multipath configuration

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

1. To view the DM-Multipath configuration, enter multipath -v3 -d -ll
   The -d (dry run) parameter prevents the command from updating the multipath maps.
2. Verify that the multipathd is running:
   • For Red Hat Enterprise Linux 6 and 5 series, use the /etc/init.d/multipathd status command.
   • For Red Hat Enterprise Linux 7 series, use the systemctl status multipathd command.
3. To determine whether 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.
4. View a list of the multipath devices, including which /dev/sdx devices are used: multipath -ll
   The multipath -ll command output varies slightly across Linux versions, as shown in the following examples.
   Example
   Red Hat Enterprise Linux 5.11:

   # multipath -ll
   3600a098041757765662444434256557a dm-11 NETAPP,LUN C-Mode
   [size=10G][features=3 queue_if_no_path pg_init_retries 50][hwhandler=1 alua][rw]
   \_ round-robin 0 [prio=50][active]
    \_ 7:0:6:3  sdco 69:192 [active][ready]
    \_ 7:0:1:3  sdbu 68:128 [active][ready]
    \_ 8:0:14:3 sdbi 67:192 [active][ready]
    \_ 8:0:13:3 sdbe 67:128 [active][ready]
   \_ round-robin 0 [prio=10][enabled]
    \_ 8:0:7:3  sdag 66:0   [active][ready]
    \_ 8:0:15:3 sdbm 68:0   [active][ready]
    \_ 7:0:3:3  sdcc 69:0   [active][ready]
    \_ 7:0:15:3 sddy 128:0  [active][ready]

   Example
   Red Hat Enterprise Linux 6.6:

   # multipath -ll
   3600a0980383034586b3f4644694d6a51 dm-14 NETAPP,LUN C-Mode
   size=5.0G features='4 queue_if_no_path pg_init_retries 50 retain_attached_hw_handle' hwhandler='1 alua' wp=rw
   |-+- policy='round-robin 0' prio=50 status=active
   | |- 0:0:10:11 sdxq  128:512  active ready running
   | |- 1:0:5:11  sdxn  71:720   active ready running
   | |- 0:0:2:11  sdcq  69:224   active ready running
   | `- 1:0:8:11  sdafa 68:768   active ready running
   `-+- policy='round-robin 0' prio=10 status=enabled
     |- 0:0:8:11  sdrg  133:416  active ready running
     |- 1:0:10:11 sdaie 129:800  active ready running
     |- 0:0:11:11 sdaau 133:544  active ready running
     `- 1:0:11:11 sdajt 131:944  active ready running
   

   Example
   FC on Red Hat Enterprise Linux 7.0:

   # multipath -ll
   3600a09804d542d4d71244635712f4a4a dm-20 NETAPP  ,LUN C-Mode
   size=5.0G features='4 queue_if_no_path pg_init_retries 50 retain_attached_hw_handle' hwhandler='1 alua' 
   wp=rw
   |-+- policy='service-time 0' prio=50 status=active
   | |- 4:0:3:21 sdeo 129:0   active ready running
   | |- 4:0:7:21 sdnj 71:336  active ready running
   | |- 5:0:5:21 sdui 66:672  active ready running
   | `- 5:0:7:21 sdxm 71:704  active ready running
   `-+- policy='service-time 0' prio=10 status=enabled
     |- 4:0:5:21 sdhs 134:32  active ready running
     |- 4:0:6:21 sdks 67:256  active ready running
     |- 5:0:4:21 sdst 8:528   active ready running
     `- 5:0:6:21 sdvx 69:560  active ready running

   Example
   SLES11 SP3:

   # multipath -ll
   3600a09804d542d4d71244635712f4a4a dm-20 NETAPP  ,LUN C-Mode
   size=5.0G features='4 queue_if_no_path pg_init_retries 50 retain_attached_hw_handle' hwhandler='1 alua' 
   wp=rw
   |-+- policy='service-time 0' prio=50 status=active
   | |- 4:0:3:21 sdeo 129:0   active ready running
   | |- 4:0:7:21 sdnj 71:336  active ready running
   | |- 5:0:5:21 sdui 66:672  active ready running
   | `- 5:0:7:21 sdxm 71:704  active ready running
   `-+- policy='service-time 0' prio=10 status=enabled
     |- 4:0:5:21 sdhs 134:32  active ready running
     |- 4:0:6:21 sdks 67:256  active ready running
     |- 5:0:4:21 sdst 8:528   active ready running
     `- 5:0:6:21 sdvx 69:560  active ready running

   Example
   FC on Red Hat Enterprise Virtualization Hypervisor 6.2 with ALUA enabled:

   # 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
   

5. You can verify that the NetApp recommended DM-Multipath settings are currently in use by entering the following commands:
   • For RHEL6 and 7 hosts, use the multipathd show config command.
     • For RHEL5 hosts, use the multipathd -k"show config" command.
   • For SLES11 hosts, use the multipathd show config command.

   For details about the commands, see the man pages.

6. If you want to view the /dev/mapper devices: ls -l /dev/mapper/
   Example
   The following example shows the 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