Example: even-nodes cluster

    +-------------------------------------------+                                
    |  site3                                    |                                
    |                                           |                                
    |  +-------------+                          |
    |  |             |                          |
    |  | arbitrator1 |                          |
    |  |             |                          |
    |  +-------------+                          |
    |                                           |                                
    +-------------------------------------------+                                
    
    +--------------------------+     +------------------------------+
    | site1                    |     |   site2                      |
    |                          |     |                              |
    |    +---------------------|-----|-----------------------+      |
    |    | cluster             |     |                       |      |
    |    |                     |     |                       |      |
    |    |    +-----------+    |     |   +-----------+       |      |
    |    |    |           |    |     |   |           |       |      |
    |    |    |   node1   |    |     |   |   node2   |       |      |
    |    |    |           |    |     |   |           |       |      |
    |    |    +-----------+    |     |   +-----------+       |      |
    |    |                     |     |                       |      |
    |    +---------------------|-----|-----------------------+      |
    |                          |     |                              |
    +--------------------------+     +------------------------------+
  • Total: 3 votes
  • Majority: 2 votes

Site1 Isolated

node1 standpoint

  • live nodes: 1 (node1)
  • arbitrators votes: 0
  • votes: 1

=> node does not have quorum, commits suicide

node2 standpoint

  • live nodes: 1 (node2)
  • arbitrators votes: 1
  • votes: 2

=> node has quorum, does not commit suicide

Node1 dies

node2 standpoint

  • live nodes: 1 (node2)
  • arbitrators votes: 1
  • votes: 2

=> node has quorum, does not commit suicide