Some machines have local SCSI cards for their internal disks. DM-Multipath is not recommended for these devices. The following procedure shows how to modify the multipath configuration file to ignore the local disks when configuring multipath.

Find out which disks are the internal disks

One quick way is to run the multipath -v2 shows the local disk. In this example, /dev/sda is the internal disk. For further information on the multipath command output.

    # multipath -v2
    Jun 19 23:45:28 | sda: rdac prio: inquiry command indicates error
    create: SATA_A2_LUN15 (360080e50001818f80000138354ee1291) undef IBM     ,1814      FAStT
    size=500G features='1 queue_if_no_path' hwhandler='1 rdac' wp=undef
    |-+- policy='round-robin 0' prio=14 status=undef
    | |- 3:0:0:14 sdh  8:112  undef ready  running
    | `- 4:0:1:14 sdaw 67:0   undef ready  running
    `-+- policy='round-robin 0' prio=9 status=undef
      |- 3:0:1:14 sdaj 66:48  undef ready  running
      `- 4:0:0:14 sdu  65:64  undef ready  running
    ...

You can also use other ways, for example, use scsi_id to identify disk Vendor and type. Or, use internal controller card tool to identify.

Blacklist localdisk in multipath

In order to prevent the device mapper from mapping /dev/sda in its multipath maps, edit the blacklist section of the /etc/multipath.conf file to include this device.

There are 3 rules in multipath blacklist section to blacklist a device in multipath blacklist:

    device node rules
    wwid rule
   device rule

Although you could use device node rule to blacklist the sda device, but that would not be safe procedure since /dev/sda is not guaranteed to be the same on reboot. Safer to use either WWID rule or device rule

Note: in the output to the multipath -v2 command, the WWID of the /dev/sda device is SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1.

To blacklist this device, include the following in the /etc/multipath.conf file.

Use WWID rule

    blacklist {
          wwid SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1
    }

Or use device rule

blacklist {
        device {
                vendor "ServeRA"
        }
}

Or use device node rule

blacklist {
    devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
}

Reload multipath config file

After you have updated the /etc/multipath.conf file, you must manually tell the multipathd daemon to reload the file. The following command reloads the updated /etc/multipath.conf file.

    # systemctl reload multipath-tools.service

Remove multipath device

Run the following command to remove the multipath device:

    # multipath -f SIBM-ESXSST336732LC____F3ET0EP0Q000072428BX1

To check whether the device removal worked, you can run the multipath -ll command to display the current multipath configuration. To check that the blacklisted device was not added back, you can run the multipath command, as in the following example. The multipath command defaults to a verbosity level of v2 if you do not specify a -v option.

    # multipath -ll
    SATA_LUN19 (360080e50001818f80000138754ee12d6) dm-8 IBM     ,1814      FAStT
    size=500G features='1 queue_if_no_path' hwhandler='1 rdac' wp=rw
    |-+- policy='round-robin 0' prio=14 status=active
    | |- 3:0:0:18 sdp  8:240  active ready running
    | `- 4:0:1:18 sdbb 67:80  active ready running
    `-+- policy='round-robin 0' prio=9 status=enabled
      |- 3:0:1:18 sdar 66:176 active ready running
      `- 4:0:0:18 sdaa 65:160 active ready running
    SATA_LUN21 (360080e50001818f80000138954ee130c) dm-10 IBM     ,1814      FAStT
    size=625G features='1 queue_if_no_path' hwhandler='1 rdac' wp=rw
    |-+- policy='round-robin 0' prio=14 status=active
    | |- 3:0:0:20 sdt  65:48  active ready running
    | `- 4:0:1:20 sdbd 67:112 active ready running
    `-+- policy='round-robin 0' prio=9 status=enabled
      |- 3:0:1:20 sdav 66:240 active ready running
      `- 4:0:0:20 sdae 65:224 active ready running
    SATA_LUN20 (360080e50001818f40000137154ee0c7f) dm-9 IBM     ,1814      FAStT
    size=600G features='1 queue_if_no_path' hwhandler='1 rdac' wp=rw
    |-+- policy='round-robin 0' prio=14 status=active
    | |- 3:0:1:19 sdat 66:208 active ready running
    | `- 4:0:0:19 sdac 65:192 active ready running
    `-+- policy='round-robin 0' prio=9 status=enabled
      |- 3:0:0:19 sdr  65:16  active ready running
      `- 4:0:1:19 sdbc 67:96  active ready running