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Deploy Three Config Servers for Production Deployments

Deploy Three Config Servers for Production Deployments¶

This procedure converts a test deployment with only one config server to a production deployment with three config servers.

Tip

Use CNAMEs to identify your config servers to the cluster so that you can rename and renumber your config servers without downtime.

For redundancy, all production sharded clusters should deploy three config servers on three different machines. Use a single config server only for testing deployments, never for production deployments. When you shift to production, upgrade immediately to three config servers.

To convert a test deployment with one config server to a production deployment with three config servers:

Shut down all existing MongoDB processes in the cluster. This includes:
- all mongod instances or replica sets that provide your shards.
- all mongos instances in your cluster.
Copy the entire dbpath file system tree from the existing config server to the two machines that will provide the additional config servers. These commands, issued on the system with the existing Config Database, mongo-config0.example.net may resemble the following:
copy
```
rsync -az /data/configdb mongo-config1.example.net:/data/configdb
rsync -az /data/configdb mongo-config2.example.net:/data/configdb
```
Start all three config servers, using the same invocation that you used for the single config server.
copy
```
mongod --configsvr
```
Restart all shard mongod and mongos processes.

When restarting mongos processes, update the --configdb option to include all three config servers. The mongos processes must specify the same configdb string, with identical host names listed in identical order. For example:
copy
```
mongos --configdb mongo-config0.example.net,mongo-config1.example.net,mongo-config2.example.net
```

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