See also: 

Security Deployment Tutorials (page 353) for additional related tutorials. 

Deploy a Replica Set (page 603) Configure a three-member replica set for production systems. 

Deploy a Replica Set for Testing and Development (page 605) Configure a three-member replica set for either de- velopment or testing systems. 

Deploy a Geographically Redundant Replica Set (page 608) Create a geographically redundant replica set to protect against location-centered availability limitations (e.g. network and power interruptions). 

Add an Arbiter to Replica Set (page 614) Add an arbiter give a replica set an odd number of voting members to prevent election ties. 

Convert a Standalone to a Replica Set (page 614) Convert an existing standalone mongod instance into a three- member replica set. 

Add Members to a Replica Set (page 616) Add a new member to an existing replica set. 

Remove Members from Replica Set (page 618) Remove a member from a replica set. 

Replace a Replica Set Member (page 620) Update the replica set configuration when the hostname of a member’s corresponding mongod instance has changed. 

## Deploy a Replica Set 

This tutorial describes how to create a three-member replica set from three existing mongod instances running with access control (page 324) disabled. 

To deploy a replica set with enabled access control (page 324), see Deploy Replica Set and Configure Authentication and Authorization (page 353). If you wish to deploy a replica set from a single MongoDB instance, see Convert a Standalone to a Replica Set (page 614). For more information on replica set deployments, see the Replication (page 559) and Replica Set Deployment Architectures (page 572) documentation. 

## Overview 

Three member replica sets provide enough redundancy to survive most network partitions and other system failures. These sets also have sufficient capacity for many distributed read operations. Replica sets should always have an odd number of members. This ensures that elections (page 580) will proceed smoothly. For more about designing replica sets, see the Replication overview (page 559). 

The basic procedure is to start the mongod instances that will become members of the replica set, configure the replica set itself, and then add the mongod instances to it. 

## Requirements 

For production deployments, you should maintain as much separation between members as possible by hosting the mongod instances on separate machines. When using virtual machines for production deployments, you should place each mongod instance on a separate host server serviced by redundant power circuits and redundant network paths. 

Before you can deploy a replica set, you must install MongoDB on each system that will be part of your replica set . If you have not already installed MongoDB, see the installation tutorials (page 5). 

Before creating your replica set, you should verify that your network configuration allows all possible connections between each member. For a successful replica set deployment, every member must be able to connect to every other member. For instructions on how to check your connection, see Test Connections Between all Members (page 648). 

