DOCS-326 correcting the text to refer to the new migration threshold section.

Author: Sam Kleinman

source/administration/sharding.txt

@@ -974,11 +974,11 @@ sense. Sharding works by migrating chunks between the shards until
 each shard has roughly the same number of chunks.
 
 The default chunk size is 64 megabytes. MongoDB will not begin
-migrations until the shard with the most chunks has 8 more chunks than
-the shard with the fewest chunks. While the default chunk size is
-configurable with the :setting:`chunkSize` setting, these behaviors
-help prevent unnecessary chunk migrations, which can degrade the
-performance of your cluster as a whole.
+migrations until the imbalance of chunks in the cluster exceeds the
+:ref:`migration threshold <sharding-migration-thresholds>`. While the
+default chunk size is configurable with the :setting:`chunkSize`
+setting, these behaviors help prevent unnecessary chunk migrations,
+which can degrade the performance of your cluster as a whole.
 
 If you have just deployed a shard cluster, make sure that you have
 enough data to make sharding effective. If you do not have sufficient

source/core/sharding-internals.txt

@@ -333,15 +333,14 @@ chunks in a collection is unevenly distributed among the shards, the
 balancer begins migrating :term:`chunks <chunk>` from shards with more
 chunks to shards with a fewer number of chunks. The balancer will
 continue migrating chunks, one at a time, until the data is evenly
-distributed among the shards. See the :ref:`migration thresholds
-<sharding-migration-thresholds>` section for more information.
+distributed among the shards.
 
 While these automatic chunk migrations are crucial for distributing
 data, they carry some overhead in terms of bandwidth and workload,
 both of which can impact database performance. As a result, MongoDB
 attempts to minimize the effect of balancing by only migrating chunks
-when the difference between the number of chunks on shards are greater
-than 8.
+when the distribution of chunks passes the :ref:`migration thresholds
+<sharding-migration-thresholds>`.
 
 .. index:: balancing; migration
 

source/core/sharding.txt

@@ -191,18 +191,17 @@ Data
 Your cluster must manage a significant quantity of data for sharding
 to have an effect on your collection. The default :term:`chunk` size
 is 64 megabytes, [#chunk-size]_ and the :ref:`balancer
-<sharding-balancing>` will not begin moving data until the shard with
-the greatest number of chunks has *8 more* chunks than the shard with
-least number of chunks.
-
-Practically, this means that unless there is 512 megabytes of data,
-all of the data will remain on the same shard. You can set a smaller
-chunk size, or :ref:`manually create splits in your collection
-<sharding-procedure-create-split>` using the :func:`sh.splitFind()` and
-:func:`sh.splitAt()` operations in the :program:`mongo` shell.
-Remember that the default chunk size and migration threshold
-are explicitly configured to prevent unnecessary splitting or
-migrations.
+<sharding-balancing>` will not begin moving data until the imbalance
+of chunks in the cluster exceeds the :ref:`migration threshold
+<sharding-migration-thresholds>`.
+
+Practically, this means that unless your cluster has enough data,
+chunks will remain on the same shard. You can set a smaller chunk
+size, or :ref:`manually create splits in your collection
+<sharding-procedure-create-split>` using the :func:`sh.splitFind()`
+and :func:`sh.splitAt()` operations in the :program:`mongo` shell.
+Remember that the default chunk size and migration threshold are
+explicitly configured to prevent unnecessary splitting or migrations.
 
 While there are some exceptional situations where you may need to
 shard a small collection of data, most of the time the additional
@@ -453,9 +452,10 @@ have on the cluster, by:
 
 - Only moving one chunk at a time.
 
-- Only initiating a balancing round if there is a difference of *more
-  than* 8 chunks between the shard with the greatest and the shard with
-  the least number of chunks.
+- Only initiating a balancing round when the difference in number of
+  chunks between the shard with the greatest and the shard with the
+  least number of chunks exceeds the :ref:`migration threshold
+  <sharding-migration-thresholds>`.
 
 Additionally, it's possible to disable the balancer on a temporary
 basis for maintenance and limit the window during which it runs to