HP-UX HB v13.00 Ch-15 - Serviceguard

HP-UX Handbook – Rev 13.00 Page 14 (of 108)
Chapter 15 Serviceguard
October 29, 2013
Quorum Rules:
 Nodes that continue to exchange heartbeat messages in a greater than 50% subset of the
previous cluster will reform a new cluster. The arbitration device will not be used. Example:
If 2 nodes cannot exchange HB with a 3
rd
node, the 2 nodes will reform a cluster and adopt
node 3 packages. Node 3 will automatically TOC (see next rule).
 Nodes that can only exchange heartbeat messages in a less than 50% subset of the previous
cluster are forced to TOC to preserve data integrity, under the assumption that the packages
will be managed by other nodes forming a majority. Example: If 1 node cannot exchange
HB with 2 other nodes, the node will TOC.
 When exactly 50% of nodes cannot interact with the other half (a split-brain condition), they
must negotiate with the arbitration device (cluster lock disk, lock LUN or Quorum Server) to
decide which half forms the new cluster and which half TOCs. Example: If 1 node cannot
exchange HB with its partner node, they both seek the arbitration device. The first node to
attain abitration reforms the cluster and the late one performs a TOC.
 If no node can reach the cluster arbitration device, all nodes TOC.