Installation guide

Table 4 .1. Multipath Configuration Default s
Attribute Description
udev_dir Specifies the directory where udev device nodes are created. T he
default value is /udev.
polling_interval Specifies the interval between two path checks in seconds. T he
default value is 5.
selector Specifies the default algorithm to use in determining what path to
use for the next I/O operation. T he 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
m ultibus = 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 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. T he
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. T he default value is (null).
path_checker Specifies the default method used to determine the state of the
paths. Possible values include: readsector0, tur,
em c_clariion, hp_sw, and directio. T he default value is
readsector0.
failback Specifies path group failback.
A value of 0 or im m ediate specifies that as soon as there is a
path group with 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 m anual specifies that failback can happen only with
operator intervention.
The default value is manual.
Red Hat Enterprise Linux 4 DM Multipath
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