DOCS-7315 replica set architectures (#2444)

* DOCS-7315

* DOCS-7315 update load balance section

* Staging fixes

Author: Dave Cuthbert

source/core/replica-set-architectures.txt

@@ -121,17 +121,18 @@ Add :ref:`hidden <replica-set-hidden-members>` or :ref:`delayed
 <replica-set-delayed-members>` members to support dedicated functions,
 such as backup or reporting.
 
-Load Balance on Read-Heavy Deployments
-``````````````````````````````````````
+Read-Heavy Applications
+```````````````````````
 
-In a deployment with *very* high read traffic, you can improve read
-throughput by distributing reads to secondary members. As your
-deployment grows, add or move members to alternate data centers to
-improve redundancy and availability.
+A replica set is designed for high availability and redundancy. In most
+cases secondary members operate under similar loads as the primary. You
+should not direct reads to secondaries. 
 
-.. include:: /includes/note-csrs-distribution.rst
+If you have a read-heavy application, consider using :ref:`c2c-index` to
+replicate data to another cluster for reading.  
 
-Always ensure that the main facility is able to elect a primary.
+For more information on secondary read modes, see: :readmode:`secondary`
+and :readmode:`secondaryPreferred`.
 
 Add Capacity Ahead of Demand
 ````````````````````````````