adding in line to link with Chunk Migration and Create Chunk section

Author: Andrew Leung

source/administration/sharding.txt

@@ -626,6 +626,11 @@ However, you may want to migrate chunks manually in a few cases:
 - If the balancer in an active cluster cannot distribute chunks within
   the balancing window, then you will have to migrate chunks manually.
 
+To further understand the chunk migration process in detail, see the
+:ref:`sharding-chunk-migration` section, and how to improve throughput
+for a shard cluster, see the
+:ref:`sharding-administration-create-chunks` section.
+
 To migrate chunks, use the :dbcommand:`moveChunk` command.
 
 .. note::