DOCS-153 all config servers must be up to init cluster

Author: Ed Costello

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/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