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How can I avoid fencing loops with 2 node clusters and Red Hat High Availability clusters?

Updated 2014-04-18T20:03:42+00:00

Issue

  • Why should I have my fencing devices on the same network as my cluster communication with Red Hat High Availability clusters?
  • How can I prevent fence loops with my cluster?
  • If one node in a 2-node cluster is up and running, and the other node boots up while there is a network issue, that booting node fences the active node
  • In a 2-node cluster configured with fence_scsi, if a node gets fenced due to a network issue and I then reboot it, the "active" node reports SCSI reservation conflicts and path failures as the rebooted node starts its services.

Environment

  • Red Hat Enterprise Linux (RHEL), including
    • Red Hat Enterprise Linux Server 5 (with the High Availability Add on)
    • Red Hat Enterprise Linux Server 6 (with the High Availability Add on)
  • Red Hat High Availability Cluster with 2 nodes (this issue does not apply to 3 or more node clusters.
  • No quorum disk is configured. Cluster must have only 2 votes with two_node="1" set.
  • Cluster fencing devices are IP-based and are accessed over the network.
    • Fencing devices are reached over a different network to the network that the cluster communicates over
      • This effectively means both nodes can reach the fencing devices when the cluster interconnect is unavailable.

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