Installation guide

Table 4 .2. Multipath Attribut es
Attribute Description
wwid Specifies the WWID of the multipath device to which the
m ultipath attributes apply.
alias Specifies the symbolic name for the multipath device to which the
m ultipath attributes apply.
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
path_selector Specifies the default algorithm to use in determining what path to
use for the next I/O operation.
rr_min_io (RHEL 4.8 and later) Specifies the number of I/O requests to route
to a path before switching to the next path in the current path
group.
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.
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_m in_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.
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 queueing.
A value of queue indicates that queuing should not stop until the
path is fixed.
Chapter 4. The DM-Multipath Configuration File
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