Replica Sets

Overview

Replica sets are a form of asynchronous master/slave replication, adding automatic failover and automatic recovery of member nodes.

  • A replica set consists of two or more nodes that are copies of each other. (i.e.: replicas)
  • The replica set automatically elects a primary (master). No one member is intrinsically primary; that is, this is a share-nothing design.
  • Drivers (and mongos) can automatically detect when a replica set primary changes and will begin sending writes to the new primary. (The mongos sharding process does this too.)

Replica sets have several common uses:

  • Data Redundancy
  • Automated Failover / High Availability
  • Distributing read load
  • Simplify maintenance (compared to "normal" master-slave)
  • Disaster recovery

Getting started

Operation

Advanced and More

How-tos

Troubleshooting

See Also

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