Novell LINUX ENTERPRISE SERVER 10 SP3 - ARCHITECTURE-SPECIFIC, Administration Manual, Page: 63 / 132

Managing Multipath I/O for Devices 63
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prio_callout Specifies the program and
arguments to use to
determine the layout of the
multipath map.
When queried by the
multipath
command, the
specified mpath_prio_*
callout program returns the
priority for a given path in
relation to the entire multipath
layout.
When it is used with the
path_grouping_policy of
group_by_prio, all paths with
the same priority are grouped
into one multipath group. The
group with the highest
aggregate priority becomes
the active group.
When all paths in a group fail,
the group with the next
highest aggregate priority
becomes active. Additionally,
a failover command (as
determined by the hardware
handler) might be send to the
target.
The mpath_prio_* program
can also be a custom script
created by a vendor or
administrator for a specified
setup.
A %n in the command line
expands to the device name
in the
/dev directory.
A %b expands to the device
number in
major:minor format
in the
/dev
directory.
A %d expands to the device
ID in the
/dev/disk/by-id
directory.
If devices are hot-pluggable,
use the %d flag instead of
%n. This addresses the short
time that elapses between the
time when devices are
available and when
udev
creates the device nodes.
If no prio_callout attribute is used, all paths
are equal. This is the default.
/bin/true Use this value when the
group_by_priority is not being used.
The
prioritizer
programs generate path priorities
when queried by the
multipath
command. The
program names must begin with mpath_prio_
and are named by the device type or balancing
method used. Current prioritizer programs
include the following:
/sbin/mpath_prio_alua %n Generates path
priorities based on the SCSI-3 ALUA settings.
/sbin/mpath_prio_balance_units Generates
the same priority for all paths.
/sbin/mpath_prio_emc %n Generates the path
priority for EMC arrays.
/sbin/mpath_prio_hds_modular %b
Generates the path priority for Hitachi HDS
Modular storage arrays.
/sbin/mpath_prio_hp_sw %n Generates the
path priority for Compaq/HP controller in active/
standby mode.
/sbin/mpath_prio_netapp %n Generates the
path priority for NetApp arrays.
/sbin/mpath_prio_random %n Generates a
random priority for each path.
/sbin/mpath_prio_rdac %n Generates the path
priority for LSI/Engenio RDAC controller.
/sbin/mpath_prio_tpc %n You can optionally
use a script created by a vendor or administrator
that gets the priorities from a file where you
specify priorities to use for each path.
/usr/local/sbin/mpath_prio_spec.sh %n
Provides the path of a user-created script that
generates the priorities for multipathing based on
information contained in a second data file. (This
path and filename are provided as an example.
Specify the location of your script instead.) The
script can be created by a vendor or
administrator. The script’s target file identifies
each path for all multipathed devices and
specifies a priority for each path. For an
example, see
Section 5.6.3, “Using a Script to
Set Path Priorities,” on page 65 .
Multipath Attribute Description Values