These documents describe and provide examples of replica set
operation, configuration, and behavior. For an overview of
replication, see Replication Introduction. For
documentation of the administration of replica sets, see
Replica Set Tutorials. The Replication Reference
documents commands and operations specific to replica sets.
- Replica Set Members
Introduces the components of replica sets.
- Replica Set Primary
- The primary is the only member of a replica set that accepts write operations.
- Replica Set Secondary Members
- Secondary members replicate the primary’s data set and accept read
operations. If the set has no primary, a secondary can become primary.
- Priority 0 Replica Set Members
- Priority 0 members are secondaries that cannot become the primary.
- Hidden Replica Set Members
- Hidden members are secondaries that are invisible to
applications. These members support dedicated workloads, such as
reporting or backup.
- Replica Set Arbiter
- An arbiter does not maintain a copy of the data set but participate
- Replica Set Deployment Architectures
Introduces architectural considerations related to
replica sets deployment planning.
- Three Member Replica Sets
- Three-member replica sets provide the minimum
recommended architecture for a replica set.
- Replica Sets with Four or More Members
- Four or more member replica sets provide
greater redundancy and can support greater distribution of read
operations and dedicated functionality.
- Replica Set High Availability
Presents the details of the automatic failover and recovery process
with replica sets.
- Replica Set Elections
- Elections occur when the primary becomes unavailable and the
replica set members autonomously select a new primary.
- Read Preference
- Applications specify read preference to control how drivers direct
read operations to members of the replica set.
- Replication Processes
- Mechanics of the replication process and related topics.
- Master Slave Replication
- Master-slave replication provided redundancy in early versions of
MongoDB. Replica sets replace master-slave for most use cases.