4.3. Configuration File Defaults

4.3. Configuration File Defaults

The /etc/multipath.conf configuration file includes a defaults section that sets the user_friendly_names parameter to yes, as follows. 

defaults {
        user_friendly_names yes
}

This overwrites the default value of the user_friendly_names parameter.

The configuration file includes a template of configuration defaults. This section is commented out, as follows. 

#defaults {
#       udev_dir                /dev
#       polling_interval        10
#       selector                "round-robin 0"
#       path_grouping_policy    multibus
#       getuid_callout          "/sbin/scsi_id -g -u -s /block/%n"
#       prio_callout            /bin/true
#       path_checker            readsector0
#       rr_min_io               100
#       rr_weight               priorities
#       failback                immediate
#       no_path_retry           fail
#       user_friendly_name      yes
#}

To overwrite the default value for any of the configuration parameters, you can copy the relevant line from this template into the defaults section and uncomment it. For example, to overwrite the path_grouping_policy parameter so that it is multibus rather than the default value of failover, copy the appropriate line from the template to the initial defaults section of the configuration file, and uncomment it, as follows. 

defaults {
        user_friendly_names     yes
        path_grouping_policy    multibus
}

Table 4.1, “Multipath Configuration Defaults” describes the attributes that are set in the defaults section of the multipath.conf configuration file. These values are used by DM-Multipath unless they are overwritten by the attributes specified in the devices and multipaths sections of the multipath.conf file.

Attribute Description
udev_dir Specifies the directory where udev device nodes are created. The default value is /udev.
polling_interval Specifies the interval between two path checks in seconds. The default value is 5.
selector Specifies the default algorithm to use in determining what path to use for the next I/O operation. The default value is round-robin 0.
path_grouping_policy Specifies the default path grouping policy to apply to unspecified multipaths. Possible values include:
failover = 1 path per priority group
multibus = all valid paths in 1 priority group
group_by_serial = 1 priority group per detected serial number
group_by_prio = 1 priority group per path priority value
group_by_node_name = 1 priority group per target node name
The default value is failover.
getuid_callout Specifies the default program and arguments to call out to obtain a unique path identifier. An absolute path is required.
The default value is /sbin/scsi_id -g -u -s.
prio_callout Specifies the the default program and arguments to call out to obtain a path priority value. For example, the ALUA bits in SPC-3 provide an exploitable prio value for example. "none" is a valid value. The default value is no callout, indicating all paths are equal
features Specifies the default extra features of multipath devices. The only existing feature is queue_if_no_path. The default value is (null).
path_checker Specifies the default method used to determine the state of the paths. Possible values include: readsector0, tur, emc_clariion, hp_sw, and directio. The default value is readsector0.
rr_min_io Specifies the number of I/O requests to route to a path before switching to the next path in the current path group. The default value is 1000.
rr_weight If set to priorities, then instead of sending rr_min_io requests to a path before calling selector to choose the next path, the number of requests to send is determined by rr_min_io times the path's priority, as determined by the prio_callout program. Currently, there are priority callouts only for devices that use the group_by_prio path grouping policy, which means that all the paths in a path group will always have the same priority.
If set to uniform, all path weights are equal. The default value is uniform.
failback Specifies path group failback.
A value of 0 or immediate specifies that as soon as there is a path group whith a higher priority than the current path group the system switches to that path group.
A numeric value greater than zero specifies deferred failback, expressed in seconds.
A value of manual specifies that failback can happen only with operator intervention.
The default value is manual.
no_path_retry A numeric value for this attribute specifies the number of times the system should attempt to use a failed path before disabling queueing.
A value of fail indicates immediate failure, without queuing.
A value of queue indicates that queuing should not stop until the path is fixed.
The default value is (null).
user_friendly_names If set to yes, specifies that the system should using the bindings file /var/lib/multipath/bindings to assign a persistent and unique alias to the multipath, in the form of mpathn. If set to no, specifies that the system should use use the WWID as the alias for the multipath. In either case, what is specified here will be overriden by any device-specific aliases you specify in the multipaths section of the configuration file. The default value is no.
bindings_file The location of the bindings file that is used with the user_friendly_names option. The default value is /var/lib/multipath/bindings.

Table 4.1. Multipath Configuration Defaults