In the Starting a simple sharded environment of two shards recipe in Chapter 1, Installing and Starting the MongoDB Server, we set up a simple two-shard server. In the Connecting to a shard from the Mongo shell and performing operations recipe in Chapter 1, Installing and Starting the MongoDB Server, we added data to a person collection that was sharded. However, for any collection that is not sharded, all the documents end up on one shard called the primary shard. This situation is acceptable for small databases with a relatively small number of collections. However, if, the database size increases and at the same time, the number of unsharded collections increase we end up overloading a particular shard (the primary shard for a database) with a lot of data from these unsharded collections. All query operations for such unsharded collections, as well as those on the collections whose particular range in the shard reside on this server...