DOCSP-31028 sharding warning (#140)

* DOCSP-31028 Adds balancer warning

* Adds restart balancer message

* Fixes per Joe

* Fixes per Joe

Author: kennethdyer

source/includes/sharding-warning.rst

@@ -0,0 +1,13 @@
+
+.. warning::
+
+   Syncing large documents to a sharded destination cluster can cause 
+   the destination cluster to initiate chunk migration.  When the destination
+   cluster migrates chunks during sync, it may trigger a bug that can result
+   in data loss.
+
+   To avoid this, it is recommended that you run the :dbcommand:`balancerStop`
+   command on the destination cluster before starting a sync.  Once ``mongosync``
+   completes the sync, you can restart the balancer with the 
+   :dbcommand:`balancerStart` command.
+

source/multiple-mongosyncs.txt

@@ -18,6 +18,8 @@ There are two ways to synchronize :ref:`sharded clusters
 loaded clusters, use multiple ``monogosync`` instances, one
 ``monogosync`` for each shard in the cluster.
 
+.. include:: /includes/sharding-warning
+
 .. _c2c-sharded-config-single:
 
 Configure a Single ``mongosync`` Instance
@@ -57,6 +59,16 @@ To configure multiple ``mongosync`` instances:
       sync, the source cluster and destination cluster must have the
       same number of shards.
 
+   .. step:: Stop the Balancer on the Destination
+
+      To stop the balancer on the destination cluster, connect to the
+      destination cluster and call the :method:`sh.stopBalancer` method:
+
+      .. code-block:: javascript
+
+         sh.stopBalancer()
+
+
    .. step:: Determine the shard IDs
 
       .. _c2c-shard-config-determine:
@@ -261,6 +273,15 @@ These commands only check progress and commit synchronization for the
 to ``progress`` and  ``commit`` on any other ``mongosync`` instances
 that may be running.
 
+Once this is done, use :method:`sh.startBalancer` to restart the balancer 
+on the destination cluster:
+
+.. code-block:: javascript
+
+   sh.startBalancer()
+
+
+
 .. _c2c-sharded-reverse:
 
 Reverse the Synchronization Direction