merge: DOCS-153

Author: Sam Kleinman

source/administration/sharding-architectures.txt

@@ -166,3 +166,7 @@ potential failure scenarios and available resolutions:
   splits <sharding-procedure-create-split>`. Replace the config server
   as soon as possible. If all multiple config databases become
   unavailable, the cluster can become inoperable.
+  
+  .. note::
+     
+     All config servers must be running when you first set up a shard cluster.

source/administration/sharding.txt

@@ -59,6 +59,10 @@ more detail or use the following procedure as a quick starting point:
    :doc:`command line </reference/mongod>` and :doc:`configuration
    file </reference/configuration-options>` options are available for config
    server instances.
+   
+.. note::
+
+   All config servers must be running when you first set up a shard cluster.
 
 #. Start a :program:`mongos` instance issuing the following command:
 
@@ -889,8 +893,10 @@ For redundancy, all production :term:`shard clusters <shard cluster>` should
 deploy three config servers processes on three different machines.
 
 Do not use only a single config server for production deployments.
-Consider deploying a single config server for testing.
-immediately. The following process shows how to upgrade from one to
+Consider deploying a single config server only for testing.
+You should upgrade to three config servers immediately if you are
+shifting to production.
+The following process shows how to upgrade from one to
 three config servers.
 
 #. Shut down all existing MongoDB processes. This includes:

source/core/sharding.txt

@@ -334,6 +334,10 @@ database. MongoDB only writes data to the config server to:
 
 - migrate a chunk between shards.
 
+Additionally, all config servers must be available on initial setup
+of a shard cluster, each :program:`mongos` instance must be able
+to write to the ``config.version`` collection.  
+
 If one or two configuration instances become unavailable, the
 cluster's metadata becomes *read only*. It is still possible to read
 and write data from the shards, but no chunk migrations or splits will