merge: DOCS-947

Author: Sam Kleinman

source/core/replication-internals.txt

@@ -10,7 +10,7 @@ normal operation or application development but may be useful for
 troubleshooting and for further understanding MongoDB's behavior and approach.
 
 For additional information about the internals of replication replica
-sets see the following resources in the MongoDB Manual: 
+sets see the following resources in the MongoDB Manual:
 
 - :doc:`/reference/local-database`
 - :doc:`/reference/replica-commands`

source/core/replication.txt

@@ -219,8 +219,8 @@ with filenames in the following form:
 .. code-block:: none
 
    <database>.<collection>.<timestamp>.bson
-   
-For example: 
+
+For example:
 
 .. code-block:: none
 
@@ -238,16 +238,16 @@ that might create rollbacks.
    megabytes of data. If your system needs to rollback more than 300
    MB, you will need to manually intervene to recover this data. If
    this is the case, you will find the following line in your
-   :program:`mongod` log: 
-            
+   :program:`mongod` log:
+
    .. code-block:: none
 
       [replica set sync] replSet syncThread: 13410 replSet too much data to roll back
 
    In these situations you will need to manually intervene to either
    save data manually, or resync from a "current" member of the set by
    deleting the content of the existing:setting:`dbpath` directory to
-   resume normal operation.   
+   resume normal operation.
 
 For more information on failover, see:
 
@@ -272,7 +272,7 @@ working with replica sets:
 
    Write concern sends a MongoDB client a response from the server to
    confirm successful write operations. In replica sets you can
-   configure :ref:`replica acknowledged <write-concern-replica-acknowledged>` 
+   configure :ref:`replica acknowledged <write-concern-replica-acknowledged>`
    write concern to ensure that secondary members of the set have
    replicated operations before the write returns.
 

source/tutorial/deploy-replica-set.txt

@@ -27,15 +27,23 @@ 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 consist of two or more :program:`mongod`
+instances. [#odd-numbered-set-sizes]_ This tutorial
+describes a three member set.  Production environments should have at
+least 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 virtual
+machines for production deployments, each member
+should live on separate host servers, served by redundant power circuits, and with
 redundant network paths.
 
+.. [#odd-numbered-set-sizes] To ensure smooth :ref:`elections
+   <replica-set-election>` always design replica sets with odd numbers
+   of members. Use :ref:`replica-set-arbiters` to ensure the set has
+   odd number of voting members and avoid tied elections.
+
 Procedure
 ---------