Red Hat DEVICE-MAPPER MULTIPATH 5.2 Configuration And Administration Manual page 32

Chapter 4. The DM-Multipath Configuration File
Attribute
getuid_callout
prio_callout
path_checker
rr_min_io
rr_weight
failback
no_path_retry
22
Description
group_by_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 method used to determine the state of
the paths. Possible values include:
,
emc_clariion hp_sw
.
readsector0
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.
If set to , then instead of sending
priorities
requests to a path before calling
path, the number of requests to send is determined by
times the path's priority, as determined by the
rr_min_io
program. Currently, there are priority callouts
prio_callout
only for devices that use the
policy, which means that all the paths in a path group will
always have the same priority.
If set to , all path weights are equal. The default value
uniform
is .
uniform
Specifies path group failback.
A value of 0 or
immediate
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 specifies that failback can happen only with
manual
operator intervention.
The default value is
immediate
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 indicates immediate failure, without queuing.
fail
= 1 priority group per target node name
.
readsector0
, and . The default value is
directio
to choose the next
selector
group_by_prio
specifies that as soon as there is a
.
.
, ,
tur
rr_min_io
path grouping