Red Hat CLUSTER SUITE 4.7 DM MULTIPATH Configuration And Administration Manual page 24

Chapter 4. The DM-Multipath Configuration File
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
path_grouping_policy
}
Table 4.1, "Multipath Configuration 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
udev_dir
polling_interval
selector
path_grouping_policy
getuid_callout
prio_callout
features
path_checker
14
yes
multibus
describes the attributes that are set in the defaults
Description
Specifies the directory where udev device nodes are created. The
default value is /udev.
Specifies the interval between two path checks in seconds. The
default value is 5.
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.
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.
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.
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
Specifies the default extra features of multipath devices. The only
existing feature is queue_if_no_path. The default value is
(null).
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.