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Convert Config Servers to a Replica Set


Feature Availability

  • For deployments running MongoDB 3.2.4 or Later.
  • Requires Ops Manager version 2.0.3 or greater.

In a sharded cluster, config servers store the metadata for the sharded cluster. For a sharded cluster to be fully operational, the config servers must be available and the metadata must be consistent across the config servers.

Beginning in MongoDB 3.2, config servers, that run the WiredTiger storage engine, can be deployed as replica sets. Running config servers as replica sets improves consistency and increases availability for the config servers.


If you have backup enabled and if you convert a sharded cluster’s config servers to a replica set, then Ops Manager Automation can no longer use snapshots created before the conversion to restore the sharded cluster. Automation can only use snapshots created after the conversion.

For new sharded cluster deployments using MongoDB 3.2, Ops Manager deploys config servers as a replica set.

For existing sharded cluster deployments that are not running config servers as replica sets, you can convert the config servers to replica sets.

You can manage config server replica sets just as you would any other replica set.


  • Ops Manager version 2.0.3 or greater.
    Ops Manager must be version 2.0.3 or greater.
  • MongoDB 3.2.4 or Later
    To convert the config servers to a replica set, the sharded cluster must be running MongoDB 3.2.4 or later versions. To upgrade the MongoDB version, see Change the Version of MongoDB.
  • Three Config Servers to Convert
    The sharded cluster must be running exactly three config servers to convert. After the conversion of the config servers to a replica set, you can add additional members to the config server replica set.
  • Write Permission for Parent Directory of dbPath
    The Automation Agent must have write permission on the parent directory of the dbPath of each config server.



During the conversion of the config servers to a replica set,

  • If the config servers use the MMAPv1 storage engine, Ops Manager changes the storage engine to WiredTiger.
  • Ops Manager creates temporary config servers, and automation eventually deletes these config servers after the conversion. However, if your Monitoring Agent should detect them at any point during the conversion, they will appear as unreachable hosts in your deployments list. After the conversion, you can safely delete them from the list. See Remove a Process from Management or Monitoring.

Upgrade your sharded cluster to MongoDB 3.2.4 or later.

If your sharded cluster is not running MongoDB 3.2.4 or later, see Change the Version of MongoDB to learn how to upgrade your cluster.


Click Deployment, then the Processes tab, then the Topology view.


Choose the Config Server to convert to a Replica Set.

  1. Click the config server icon for the sharded cluster under the Members column.
  2. Click the ellipsis h icon icon next to the config server.
  3. Select Convert Config Servers to Replica Set.

Enter a name for the new replica set.


Configure the temporary config servers.

During conversion, the Automation Agent creates temporary config servers. These temporary config servers must be network accessible from all nodes in the cluster.

During the procedure, specify distinct available ports for these temporary config servers, then click Upgrade.


Click Save.


Click Review & Deploy.


Click Confirm & Deploy.