Configuring Failover Priorities - Novell LINUX ENTERPRISE SERVER 10 SP2 - STORAGE ADMINISTRATION GUIDE 05-15-2009 Administration Manual

Policy Option
multibus
group_by_serial
group_by_prio
group_by_node_name

5.6.2 Configuring Failover Priorities

You must manually enter the failover priorities for the device in the
Examples for all settings and options can be found in the
multipath-tools/multipath.conf.annotated
"Understanding Priority Groups and Attributes" on page 60
"Configuring for Round-Robin Load Balancing" on page 64
"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
user_friendly_names
60 SLES 10 SP2: Storage Administration Guide
Description
All paths in one priority group.
One priority group per detected serial number.
One priority group per path priority value. Priorities are determined by callout
programs specified as a global, per-controller, or per-multipath option in the
etc/multipath.conf
One priority group per target node name. Target node names are fetched in the
/sys/class/fc_transport/target*/node_name
command multiplies the number of paths in a group by the
multipath
Description
Specifies whether to use IDs
or to use the /var/lib/
multipath/bindings file
to assign a persistent and
unique alias to the multipath
devices in the form of /dev/
mapper/mpathN .
configuration file.
/etc/multipath.conf
/usr/share/doc/packages/
file.
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
disk/by-id/ location.
/
location.
file.
command
/dev/