Database replication ensures redundancy, backup, and automatic failover. Replication occurs through groups of servers known as replica sets.
Consider these higher level introductions to replica sets:
The following document describes master-slave replication, which is deprecated. Use replica sets instead of master-slave in all new deployments.
For documentation of MongoDB’s operational segregation capabilities for replica set deployments see the Data Center Awareness
The following tutorials describe a number of common replica set maintenance and operational practices in greater detail.