Linux Administrator's Manual (8)
Updated: July 2006
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mpath_prio_alua - Path priority tool based on Asymmetric LUn Access
device [ device [ ... ]]
is used as a priority callout for the multipath command. It returns a number
that is used by multipath to group devices with the same priority together.
- -d directory
target directory for devices given as relative device names or devices given
Default is "/dev".
displays the command line help.
turns on verbose output. This shows all results in human readable format.
This includes information about the port group the device is in and its
shows the version number and exits.
specifies the device to query (the device must be a SCSI device that supports
the lq]Report Target Port Groupsrq] command).
One of the following three formats may be used:
The full path name that starts with '/' (e.g. /dev/sda).
The device name only. This will prefix the directory name given by the
-d option (e.g. sda).
The major and minor number of the device separated by ':'. This will
create a temporary device node in the device directory (e.g. 8:0). The
temporary name will be
The mpath_prio_alua command returns the following values:
The reason for the widely spaced priority values is the way multipath handles
them. It will multiply the number of paths in a group with the priority value
and select the group with the highest result. Thus, if there are six paths in
the active, non-optimized group and only one in the active, optimized one,
the non-optimized group would be used.
Indicates an error parsing the command line.
The given devices could not be opened for reading.
The device does not support target port groups.
The inquiry command did not return a target port group for the given device.
The report target port group command failed or did not return a target
port group that was obtained from the inquiry command.
on success. In this case the priority for the device is printed to
stdout. The priority value is:
for devices that are in the active, optimized group
for devices that are in an active but non-optimized group
for devices that are in the standby group
for all other groups
This example queries a device directly and returns the priority string:
Now the major and minor number is used to specify the device and verbose
output is selected:
#> mpath_prio_alua /dev/sda
The following example shows the entries in the devices section of the
multipath-tool configuration file (/etc/multipath.conf)
to support an IBM DS6000 storage system:
#> mpath_prio_alua -v 8:0
Target port groups are implicitly supported.
Reported target port group is 0 [active/optimized]
"/sbin/mpath_prio_alua -d/tmp %d"
Depending on your default configuration not all keywords are required
(e.g. if your path_checker is set to tur you don't have to
use the path_checker statement in the device section).
The entries for vendor and product must be strings that are 8
characters long (for vendor) and 16 characters long (for product).
The strings have to be padded with blanks if necessary.
If you are working with hotpluggable devices whose device nodes are created
by udev you should use the %d flag in the
This is because a short time elapses between the devices being available
and udev creating the device nodes.
If under certain circumstances your storage subsystem temporarily reports
failures on all paths, you should use the features statement showed
in the example.
This will configure the multipath volume to requeue I/O until a path becomes
available again, instead of reporting failures in that case.
was developed by Jan Kunigk and adapted by Stefan Bader <firstname.lastname@example.org>
- RETURN VALUE
- SEE ALSO
linux.jgfs.net manual pages