Novell LINUX ENTERPRISE 11 - HIGH AVAILABILITY, Руководство пользователя, Страница: 49 / 298

Resource Collocation
Collocational constraints that tell the cluster which resources may or may not run
together on a node.
Resource Order
Ordering constraints to define the sequence of actions.
When defining constraints, you also need to deal with scores. Scores of all kinds are
integral to how the cluster works. Practically everything from migrating a resource to
deciding which resource to stop in a degraded cluster is achieved by manipulating scores
in some way. Scores are calculated on a per-resource basis and any node with a negative
score for a resource cannot run that resource. After calculating the scores for a resource,
the cluster then chooses the node with the highest score.
INFINITY
is currently defined
as
1,000,000
. Additions or subtractions with it follows the following 3 basic rules:
• Any value + INFINITY = INFINITY
• Any value - INFINITY = -INFINITY
• INFINITY - INFINITY = -INFINITY
When defining resource constraints, you also specify a score for each constraint. The
score indicates the value you are assigning to this resource constraint. Constraints with
higher scores are applied before those with lower scores. By creating additional location
constraints with different scores for a given resource, you can specify an order for the
nodes that a resource will fail over to.
Procedure 4.4 Adding or Modifying Locational Constraints
1 Start the Linux HA Management Client and log in to the cluster as described
in Section 4.1, “Linux HA Management Client” (page 32).
2 In the Linux HA Management Client main window, click Constraints in the
left pane to see the constraints already configured for the cluster.
3 In the left pane, select Constraints and click Add.
4
Select Resource Location and click OK.
5 Enter a unique ID for the constraint. When modifying existing constraints,
the ID is already defined and is displayed in the configuration dialog.
Configuring Cluster Resources with the GUI 39