Novell LINUX ENTERPRISE SERVER 11 - STORAGE ADMINISTRATION GUIDE 2-23-2010, Руководство администратора, Страница: 65 / 140

Managing Multipath I/O for Devices 65
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prio_callout
Multipath prio_callouts
are located in shared
libraries in
/lib/
libmultipath/
lib*
. By using
shared libraries, the
callouts are loaded
into memory on
daemon startup.
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:
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
gets the priorities from a file where you specify
priorities to use for each path.
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 7.6.3, “Using a Script to
Set Path Priorities,” on page 67 .
Multipath Attribute Description Values