What are my options for avoiding fence races in RHEL 5, 6, and 7 High Availability clusters with an even number of nodes?

Solution Verified - Updated -

Issue

  • How can fence races be avoided in 2-node RHEL clusters?
  • When a network split occurs in a 2-node cluster, both nodes race to fence each other and the winner is not deterministic
  • Do I need a quorum device in a 2-node cluster to avoid fence races?
  • When I disconnect the heartbeat interface, the cluster goes completely down. The node with no cluster resources has been fenced and the node with all resources has halted itself..why?
  • With four nodes and a quorum device, I've seen that if there is a network split down the middle that creates 2 two-node partitions, both sides can race to fence each other.

Environment

  • Red Hat Enterprise Linux (RHEL) 5 or 6 with the High Availability Add On
  • A cluster with an even number of nodes
    • Two-node clusters are most commonly affected
    • Larger clusters with an even number of nodes can also be affected if using a quorum device or some other mechanism that would allow two halves of a cluster to stay quorate independently
  • Network-based fence devices that are accessed over a different network interface from that which is used for cluster communication

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