Novell LINUX ENTERPRISE SERVER 10 SP3 - STORAGE ADMINISTRATION GUIDE 2-23-2010 Administration Manual page 61

"Configuring for Single Path Failover" on page 64
"Grouping I/O Paths for Round-Robin Load Balancing" on page 64
Understanding Priority Groups and Attributes
A priority group is a collection of paths that go to the same physical LUN. By default, I/O is
distributed in a round-robin fashion across all paths in the group. The
automatically creates priority groups for each LUN in the SAN based on the path_grouping_policy
setting for that SAN. The
group's priority to determine which group is the primary. The group with the highest calculated
value is the primary. When all paths in the primary group are failed, the priority group with the next
highest value becomes active.
A path priority is an integer value assigned to a path. The higher the value, the higher is the priority.
An external program is used to assign priorities for each path. For a given device, its paths with the
same priorities belong to the same priority group.
Multipath Attributes
Table 5-5
Multipath Attribute Description
user_friendly_names Specifies whether to use IDs
or to use the
multipath/bindings
to assign a persistent and
unique alias to the multipath
devices in the form of
mapper/mpathN
blacklist Specifies the list of device
names to ignore as non-
multipathed devices, such as
cciss, fd, hd, md, dm, sr, scd,
st, ram, raw, loop.
blacklist_exceptions Specifies the list of device
names to treat as multipath
devices even if they are
included in the blacklist.
getuid The default program and
argumentss to call out to
obtain a unique path identifier.
Should be specified with an
absolute path.
command multiplies the number of paths in a group by the
multipath
/var/lib/
file
/dev/
.
multipath
Values
yes Autogenerate user-friendly names as
aliases for the multipath devices instead of the
actual ID.
no Default. Use the WWIDs shown in the
location.
disk/by-id/
For an example, see "Blacklisting Non-
Multipathed Devices in /etc/multipath.conf" on
page 58.
For an example, see the /usr/share/doc/
packages/multipath-tools/
multipath.conf.annotated
/sbin/scsi_id -g -u -s /block/%n
This is the default location and arguments.
Example:
getuid "/sbin/scsi_id -g -u -d /dev/
%n"
Managing Multipath I/O for Devices
command
/dev/
file.
61