Red Hat DEVICE-MAPPER MULTIPATH 5.2, Configuration And Administration Manual

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Attribute Description
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
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
immediate
.
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.
Chapter 4. The DM-Multipath Configuration File
22