Novell LINUX ENTERPRISE SERVER 11 - STORAGE ADMINISTRATION GUIDE 2-23-2010 Administration Manual page 65

Multipath Attribute Description
prio_callout Specifies the program and
arguments to use to
Multipath prio_callouts
determine the layout of the
are located in shared
multipath map.
libraries in /lib/
libmultipath/ When queried by the
lib* . By using multipath
shared libraries, the specified mpath_prio_*
callouts are loaded callout program returns the
into memory on priority for a given path in
daemon startup. 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
A %b expands to the device
number in major:minor format
in the
A %d expands to the device
ID in the
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
creates the device nodes.
Values
If no
are equal. This is the default.
/bin/true: Use this value when the
group_by_priority is not being used.
The
command, the
priorities when queried by the
command. The program names must begin with
mpath_prio_
type or balancing method used. Current
prioritizer programs include the following:
mpath_prio_alua %n: Generates path priorities
based on the SCSI-3 ALUA settings.
mpath_prio_balance_units: Generates the
same priority for all paths.
mpath_prio_emc %n: Generates the path
priority for EMC arrays.
mpath_prio_hds_modular %b: Generates the
path priority for Hitachi HDS Modular storage
arrays.
mpath_prio_hp_sw %n: Generates the path
priority for Compaq/HP controller in active/
standby mode.
mpath_prio_netapp %n: Generates the path
priority for NetApp arrays.
mpath_prio_random %n: Generates a random
priority for each path.
mpath_prio_rdac %n: Generates the path
priority for LSI/Engenio RDAC controller.
mpath_prio_tpc %n: You can optionally use a
script created by a vendor or administrator that
directory.
/dev
gets the priorities from a file where you specify
priorities to use for each path.
mpath_prio_spec.sh %n: Provides the path of
/dev directory.
a user-created script that generates the priorities
for multipathing based on information contained
in a second data file. (This path and filename are
/dev/disk/by-id
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
Set Path Priorities," on page
udev
attribute is used, all paths
prio_callout
prioritizer programs generate path
multipath
and are named by the device
Section 7.6.3, "Using a Script to
67.
Managing Multipath I/O for Devices 65