MongoDB Documentation, Release 3.0.4 var prefix = String.fromCharCode(x) + String.fromCharCode(y); db.adminCommand({moveChunk : "myapp.users", find : {email : prefix}, to : shServer[(y- 97)/6]}) } } --- Sharding Status --- sharding version: { "_id" : 1, "version" : 4, 725 10.3. Sharded Cluster Tutorials See Create Chunks in a Sharded Cluster (page 722) for an introduction to pre-splitting. New in version 2.2: The moveChunk command has the: _secondaryThrottle parameter. When set to true , MongoDB ensures that changes to shards as part of chunk migrations replicate to secondaries throughout the migration operation. For more information, see Change Replication Behavior for Chunk Migration (page 714). Changed in version 2.4: In 2.4, _secondaryThrottle is true by default. Warning: The moveChunk command may produce the following error message: The collection's metadata lock is already taken. This occurs when clients have too many open cursors that access the migrating chunk. You may either wait until the cursors complete their operations or close the cursors manually. The mergeChunks command allows you to collapse empty chunks into neighboring chunks on the same shard. A chunk is empty if it has no documents associated with its shard key range. Important: Empty chunks can make the balancer assess the cluster as properly balanced when it is not. Empty chunks can occur under various circumstances, including: This tutorial explains how to identify chunks available to merge, and how to merge those chunks with neighboring chunks. Note: Examples in this procedure use a users collection in the test database , using the username filed as a shard key . Identify Chunk Ranges In the mongo shell, identify the chunk ranges with the following operation: sh.status() The output of the sh.status() will resemble the following: Merge Chunks in a Sharded Cluster Overview Procedure • If a pre-split (page 722) creates too many chunks, the distribution of data to chunks may be uneven. • If you delete many documents from a sharded collection, some chunks may no longer contain data.