MongoDB Documentation, Release 3.0.4 Step 4: For the second config server, create a new data directory for WiredTiger. Ensure that the user account running mongod has read and write permissions for the new directory. mongod with WiredTiger will not start if the --dbpath directory contains data files created with a different storage engine. Step 5: Restart the second config server with WiredTiger. Specify wiredTiger as the --storageEngine and the newly created WiredTiger data directory as the --dbpath as well as any additional options as appropriate. mongod --storageEngine wiredTiger --dbpath <newWiredTigerDBPath> --configsvr You can also specify the options in a configuration file . To specify the storage engine, use the new storage.engine setting. mongorestore <exportDataDestination> Specify additional options as appropriate. See mongorestore for available options. mongodump --out <exportDataDestination> Specify additional options as appropriate, such as username and password if running with authorization enabled. See mongodump for available options. Step 13: Export data of the first config server listed in the mongos ‘ configDB setting. Step 8: Restart the third config server. Step 7: Shut down the second config server. Step 9: Export data of the third config server. Step 6: Upload the exported data using mongorestore to the second config server. Step 10: For the third config server, create a new data directory for WiredTiger. Ensure that the user account running mongod has read and write permissions for the new directory. mongod with WiredTiger will not start if the --dbpath directory contains data files created with a different storage engine. Step 11: Restart the third config server with WiredTiger. Specify wiredTiger as the --storageEngine and the newly created WiredTiger data directory as the --dbpath as well as any additional options as appropriate. mongod --storageEngine wiredTiger --dbpath <newWiredTigerDBPath> --configsvr You can also specify the options in a configuration file . To specify the storage engine, use the new storage.engine setting. mongorestore <exportDataDestination> Specify additional options as appropriate. See mongorestore for available options Step 12: Upload the exported data using mongorestore to the third config server. Chapter 12. Release Notes 816