Update source/tutorial/deploy-replica-set.txt

source/tutorial/deploy-replica-set.txt

@@ -27,13 +27,14 @@ deployments require no additional members or configuration.
 Requirements
 ------------
 
-A replica set requires three distinct systems so that each system can run its own instance
-of :program:`mongod`. For development systems you can run all three
-instances of the :program:`mongod` process on a local system. (e.g. a
-laptop) or within a virtual instance. For production environments, you
-should endeavor to maintain as much separation between the members as possible.  For
-example, when using VMs in Production, each member should live on
-separate host servers, served by redundant power circuits, and with
+Most replica sets are made up of two or more :program:`mongod` instances. This tutorial
+will deal with a 3 member set specifically.  In a production environment, this would
+usually involve a deployment on 3 distinct systems so that each system can run its own
+instance of :program:`mongod`. For development systems you can run all three instances
+of the :program:`mongod` process on a local system. (e.g. a laptop) or within a virtual
+instance. For production environments, you should endeavor to maintain as much separation
+between the members as possible.  For example, when using VMs in Production, each member
+should live on separate host servers, served by redundant power circuits, and with
 redundant network paths.
 
 Procedure