3.3. Ignoring local disks when generating multipath devices

Procedure

1. Identify the internal disk using any known parameters such as the device’s model, path or vendor, and determine its WWID by using any one of the following options:

   • Display existing multipath devices:

     # multipath -v2 -l
     
     mpatha (WDC_WD800JD-75MSA3_WD-WMAM9FU71040) dm-2 ATA,WDC WD800JD-75MS
     size=33 GB features="0" hwhandler="0" wp=rw
     `-+- policy='round-robin 0' prio=0 status=active
       |- 0:0:0:0 sda 8:0 active undef running

   • Display additional multipath devices that DM Multipath could create:

     # multipath -v2 -d
     
     : mpatha (WDC_WD800JD-75MSA3_WD-WMAM9FU71040) dm-2 ATA,WDC WD800JD-75MS
     size=33 GB features="0" hwhandler="0" wp=undef
     `-+- policy='round-robin 0' prio=1 status=undef
       |- 0:0:0:0 sda 8:0  undef ready running

   • Display device information:

     # multipathd show paths raw format "%d %w" | grep sda
     sda WDC_WD800JD-75MSA3_WD-WMAM9FU71040

     In this example, /dev/sda is the internal disk and its WWID is WDC_WD800JD-75MSA3_WD-WMAM9FU71040.

2. Edit the blacklist section of the /etc/multipath.conf file to ignore this device, using its WWID attribute:

   blacklist {
         wwid WDC_WD800JD-75MSA3_WD-WMAM9FU71040
   }

   警告

   Although you could identify the device using its devnode parameter, such as sda, it would not be a safe procedure, because /dev/sda is not guaranteed to refer to the same device on reboot.

3. Check for any configuration errors in the /etc/multipath.conf file:

   # multipath -t > /dev/null

   To see the full report, do not discard the command output:

   # multipath -t

4. Remake the initramfs if the disk is included in initramfs. For more information, see Configuring multipathing in initramfs.

5. Reload the /etc/multipath.conf file by reconfiguring the multipathd daemon:

   # systemctl reload multipathd

   注意

   Multipath devices on top of local disks cannot be removed when in use. To ignore such device, stop all users of the device. For example, by unmounting any filesystem on top of it and deactivating any logical volumes using it. If this is not possible, you can reboot the system to remove the multipath device.

Verification

1. Verify that the internal disk is ignored and it is not displayed in the multipath output:

   • List the multipathed devices:

     # multipath -v2 -l

   • List the additional devices that DM Multipath could create:

     # multipath -v2 -d