When adding a shard to a cluster, you should always ensure that the cluster has enough capacity to support the migration without affecting legitimate production traffic.
In production environments, all shards should be replica sets.
You interact with a sharded cluster by connecting to a mongos instance.
mongo --host mongos0.example.net --port 27017
Add a shard to the cluster using the sh.addShard() method, as shown in the examples below. Issue sh.addShard() separately for each shard. If the shard is a replica set, specify the name of the replica set and specify a member of the set. In production deployments, all shards should be replica sets.
You can instead use the addShard database command, which lets you specify a name and maximum size for the shard. If you do not specify these, MongoDB automatically assigns a name and maximum size. To use the database command, see addShard.
The following are examples of adding a shard with sh.addShard():
To add a shard for a replica set named rs1 with a member running on port 27017 on mongodb0.example.net, issue the following command:
sh.addShard( "rs1/mongodb0.example.net:27017" )
Changed in version 2.0.3.
For MongoDB versions prior to 2.0.3, you must specify all members of the replica set. For example:
sh.addShard( "rs1/mongodb0.example.net:27017,mongodb1.example.net:27017,mongodb2.example.net:27017" )
To add a shard for a standalone mongod on port 27017 of mongodb0.example.net, issue the following command:
sh.addShard( "mongodb0.example.net:27017" )
It might take some time for chunks to migrate to the new shard.