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2.2. Consistent Multipath Device Names in a Cluster
When the
user_friendly_names configuration option is set to yes, the name of the multipath device is unique to a node, but it is not guaranteed to be the same on all nodes using the multipath device. Similarly, if you set the alias option for a device in the multipaths section of the multipath.conf configuration file, the name is not automatically consistent across all nodes in the cluster. This should not cause any difficulties if you use LVM to create logical devices from the multipath device, but if you require that your multipath device names be consistent in every node it is recommended that you not set the user_friendly_names option to yes and that you not configure aliases for the devices. By default, if you do not set user_friendly_names to yes or configure an alias for a device, a device name will be the WWID for the device, which is always the same.
If you want the system-defined user-friendly names to be consistent across all nodes in the cluster, however, you can follow this procedure:
- Set up all of the multipath devices on one machine.
- Disable all of your multipath devices on your other machines by running the following commands:
#
service multipathd stop#multipath -F - Copy the
bindingsfile from the first machine to all the other machines in the cluster. By default, the location of this file is/var/lib/multipath/bindings. If/varis a separate partition on your system, however, you should change this value with thebindings_fileoption in thedefaultssection of themultipath.confconfiguration file, as described in Section 4.3, “Configuration File Defaults”. This file needs to be located on your root file system partition, for example:bindings_file "/etc/multipath_bindings"
- Re-enable the
multipathddaemon on all the other machines in the cluster by running the following command:#
service multipathd start
If you add a new device, you will need to repeat this process.
Similarly, if you configure an alias for a device that you would like to be consistent across the nodes in the cluster, you should ensure that the
/etc/multipath.conf file is the same for each node in the cluster by following the same procedure:
- Configure the aliases for the multipath devices in the in the
multipath.conffile on one machine. - Disable all of your multipath devices on your other machines by running the following commands:
#
service multipathd stop#multipath -F - Copy the
/etc/multipath.conffile from the first machine to all the other machines in the cluster. - Re-enable the
multipathddaemon on all the other machines in the cluster by running the following command:#
service multipathd start
When you add a new device you will need to repeat this process.
