Red Hat Cluster Suite, Manual

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Appendix C.
Multipath-usage.txt
File for Red Hat Enterprise Linux 4
Update 3
"devnode_blacklist", and "devices" sections of the
configuration file. To see what these are, refer to the
following file:
/usr/share/doc/device-mapper-multipathd-0.4.5/multipath.conf.synthetic
If you are using one of the storage arrays listed in the preceding
text (in "Overview"), you probably do not need to modify the "devices"
subsection. If you are using a simple disk enclosure, the defaults
should work. If you are using a storage array that is not
listed, you may need to create a "devices" subsection for your array.
Explanation of output
-----------------------
When you create, modify, or list a multipath device, you get a
printout of the current device setup. The format is as follows.
For each multipath device:
action_if_any: alias (wwid_if_different_from_alias)
[size][features][hardware_handler]
For each path group:
\_ scheduling_policy [path_group_priority_if_known]
[path_group_status_if_known]
For each path:
\_ host:channel:id:lun devnode major:minor [path_status]
[dm_status_if_known]
NOTE: The preceding lines for path group and path
were broken because of print limitations.
The dm status (dm_status_if_known) is like the path status
(path_status), but from the kernel’s point of view.
The dm status
has two states: "failed", which is analogous to "faulty",
and "active" which covers all other path states. Occasionally,
the path state and the dm state of a device will temporarily
not agree.
NOTE: When a multipath device is being created or modified, the
path group status and the dm status are not known.
Also, the
features are not always correct. When a multipath device is being
isted, the path group priority is not known.
Restrictions
---------------