Though MongoDB does a good job by default of splitting and migrating chunks across shards to maintain the balance, under some circumstances, such as a small number of documents or a relatively large number of small documents, where the automatic balancer doesn't split the collection, an administrator might want to split and migrate the chunks manually. In this recipe, we will see how to split and migrate the collection manually across shards. Again, for this recipe, we will set up a simple shard as we saw in Chapter 1, Installing and Starting the MongoDB Server.
Refer to the Starting a simple sharded environment of two shards recipe in Chapter 1, Installing and Starting the MongoDB Server, to set up and start a sharded environment. It is preferred to start a clean environment without any data in it. From the shell, connect to the started mongos process.