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Chapter 6. Resource Constraints

Table of Contents

6.1. Scores
6.1.1. Infinity Math
6.2. Deciding Which Nodes a Resource Can Run On
6.2.1. Options
6.2.2. Asymmetrical "Opt-In" Clusters
6.2.3. Symmetrical "Opt-Out" Clusters
6.2.4. What if Two Nodes Have the Same Score
6.3. Specifying the Order Resources Should Start/Stop In
6.3.1. Mandatory Ordering
6.3.2. Advisory Ordering
6.4. Placing Resources Relative to other Resources
6.4.1. Options
6.4.2. Mandatory Placement
6.4.3. Advisory Placement
6.5. Ordering Sets of Resources
6.6. Collocating Sets of Resources

6.1. Scores

Scores of all kinds are integral to how the cluster works. Practically everything from moving 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 can't run that resource. After calculating the scores for a resource, the cluster then chooses the node with the highest one.

6.1.1. Infinity Math

INFINITY is currently defined as 1,000,000 and addition/subtraction with it follows the following 3 basic rules:
  • Any value + INFINITY = INFINITY
  • Any value - INFINITY = -INFINITY