Working With the Multipathing Configuration File

Through the /etc/multipath.conf file, you can add a combination of definitions that customizes multipathing according to your system environment setup. You can obtain a commented example configuration from /usr/share/doc/device-mapper-multipath/multipath.conf.

The /etc/multipath.conf file is divided into the following typical sections:

defaults

Defines default multipath settings, which can be overridden by settings in the devices section. In turn, definitions in the devices section can be overridden by settings in the multipaths section.

blacklist

Defines devices that are excluded from multipath topology discovery. Excluded devices cannot be subsumed by a multipath device.

The example shows different ways that you can use to exclude devices: by WWID (wwid) and by device name (devnode).

blacklist_exceptions

Defines devices that are included in multipath topology discovery, even if the devices are implicitly or explicitly listed in the blacklist section.

multipaths

Defines settings for a multipath device that's identified by its WWID.

The alias attribute specifies the name of the multipath device as it will appear in /dev/mapper instead of a name based on either the WWID or the multipath group number.

devices

Defines settings for individual types of storage controller. Each controller type is identified by the vendor, product, and optional revision settings, which must match the information in sysfs for the device.

To add a storage device that DM-Multipath doesn't list as being supported, obtain the vendor, product, and revision information from the vendor, model, and rev files under /sys/block/device_name/device.

The following entries in /etc/multipath.conf would be appropriate for setting up active/passive multipathing to an iSCSI LUN with the specified WWID.

defaults {
    user_friendly_names    yes
    uid_attribute          ID_SERIAL
}

multipaths {
    multipath {
        wwid 360000970000292602744533030303730
    }
}

In this standby failover configuration, I/O continues through a remaining active network interface if a network interface fails on the iSCSI initiator.

Note:

If you edit /etc/multipath.conf, restart the multipathd service to make it re-read the file:

sudo systemctl restart multipathd

For more information about configuring entries in /etc/multipath.conf, refer to the multipath.conf(5) manual page.