Managing HP Serviceguard for Linux Ninth Edition, April 2009

NOTE: Keep the following in mind when reading the examples that follow, and when
actually configuring priorities:
1. auto_run (page 198) should be set to yes for all the packages involved; the examples
assume that it is.
2. Priorities express a ranking order, so a lower number means a higher priority (10
is a higher priority than 30, for example).
HP recommends assigning values in increments of 20 so as to leave gaps in the
sequence; otherwise you may have to shuffle all the existing priorities when
assigning priority to a new package.
no_priority, the default, is treated as a lower priority than any numerical value.
3. All packages with no_priority are by definition of equal priority, and there is
no other way to assign equal priorities; a numerical priority must be unique within
the cluster. See “priority” (page 201) for more information.
If pkg1 depends on pkg2, and pkg1’s priority is lower than or equal to pkg2’s, pkg2’s
node order dominates. Assuming pkg2’s node order is node1, node2, node3, then:
• On startup:
— pkg2 will start on node1, or node2 if node1 is not available or does not at
present meet all of its dependencies, etc.
◦ pkg1 will start on whatever node pkg2 has started on (no matter where
that node appears on pkg1’s node_name list) provided all of pkg1’s other
dependencies are met there.
◦ If the node where pkg2 has started does not meet all pkg1’s dependencies,
pkg1 will not start.
• On failover:
— If pkg2 fails on node1, pkg2 will fail over to node2 (or node3 if node2 is not
available or does not currently meet all of its dependencies, etc.)
◦ pkg1 will fail over to whatever node pkg2 has restarted on (no matter where
that node appears on pkg1’s node_name list) provided all of pkg1’s
dependencies are met there.
– If the node where pkg2 has restarted does not meet all pkg1’s
dependencies, pkg1 will not restart.
— If pkg1 fails, pkg1 will not fail over.
This is because pkg1 cannot restart on any adoptive node until pkg2 is running
there, and pkg2 is still running on the original node. pkg1 cannot drag pkg2
because it has insufficient priority to do so.
• On failback:
124 Planning and Documenting an HA Cluster