Understanding dm-Multipath Identifiers in Linux

By default, multipath devices are identified by a World Wide Identifier (WWID), which is globally unique. As an alternative, you can set the user_friendly_names attribute to yes in the /etc/multipath.conf file, which sets the multipath device to mpathN where N is the multipath group number.

The DM-Multipath tool uses two different sets of file names:

  • /dev/dm-N – Never use these device names, because they are intended to be used only by the DM-Multipath tool.
  • /dev/mapper/mpathN – Always use these device names to access the multipath devices. These names are persistent and are automatically created by device-mapper early in the boot process.

 

You can also use the alias attribute in the multipaths section of the configuration file to specify the name of a multipath device. The alias attribute overrides mpathN names.

 

Use either the /dev/mapper/mpathN name or the /dev/mapper/[alias] name when creating a partition, when creating an LVM physical volume, and when making and mounting a file system.

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