(DOCSP-25242): Added warning about read or write concerns.

Author: corryroot

source/tutorial/prepare-backing-mongodb-instances.txt

@@ -112,6 +112,15 @@ of the replica set on the same host as |onprem|.
    database loses one of the two data-bearing members, MongoDB stops
    write operations.
 
+.. warning:: Default read and write concerns
+
+   The :manual:`default MongoDB read and write concerns 
+   </reference/mongodb-defaults/>` for your MongoDB version should 
+   match the default read and write concerns for your 
+   :term:`backing databases` and your :term:`application database`. If 
+   you set a different read or write concern, you might experience data 
+   loss.
+
 .. _consider-monitoring-appdb:
 
 Application Database Monitoring