Manually migrating a chunk

To manually migrate a chunk, use the following command:

db.adminCommand( { moveChunk : DB.COLLECTION, find : QUERY, to : TARGET } )

The parameters are summarized as follows:

• DB.COLLECTION (string): This string represents the name of the database, and collection name, separated by a period.
• QUERY (JSON): You can specify a JSON document that describes the shard key field/value key pair considered the lower bound of the chunk to be migrated.
• TARGET (string): This is a string representing the shard server to which the chunk is moved.

The process of determining the best query document is identical to that described in the previous sub-section when determining a split point.

Use this command only if system performance is severely compromised. Be sure to stop the sharded cluster balancer before performing this action. It is considered a best practice to leave chunk migration to the sharded cluster balancer.

The last topic to cover is backup and restore...