Replica Set High Availability¶
Replica sets provide high availability using automatic failover. Failover allows a secondary member to become primary if primary is unavailable. Failover, in most situations does not require manual intervention.
Replica set members keep the same data set but are otherwise independent. If the primary becomes unavailable, the replica set holds an election to select a new primary. In some situations, the failover process may require a rollback. 
|||Replica sets remove “rollback” data when needed without intervention. Administrators must apply or discard rollback data manually.|