DOCS-290 update 2.2 upgrade instructions

Author: Sam Kleinman

source/release-notes/2.2.txt

@@ -18,8 +18,8 @@ Preparation
 ~~~~~~~~~~~
 
 If your MongoDB deployment uses authentication, upgrade your drivers
-(i.e. client libraries) before upgrading your :program:`mongod`
-instances.
+(i.e. client libraries) and and :program:`mongos` instances before
+upgrading your :program:`mongod` instances.
 
 .. TODO insert the following line if we eventually have a section on
    this change. See the :ref:`driver changes <2.2-driver-changes>`
@@ -29,7 +29,7 @@ Read through all release notes before upgrading, and ensure that no
 changes will affect your deployment.
 
 2.2 processes can inter-operate with 2.0 and 1.8 tools and processes
-in replica sets and shard clusters, if you are not running with
+in replica sets and sharded clusters, if you are not running with
 authentication. As a result, you can safely upgrade the
 :program:`mongod` and :program:`mongos` components of your deployment
 in any order.
@@ -75,9 +75,14 @@ Upgrading a Shard Cluster
 If your cluster uses authentication, use the following upgrade
 procedure:
 
-- Upgrade all :program:`mongos` instances first, in any order.
+- Upgrade all :program:`mongos` instances *first*, in any order.
 
-- Upgrade all other cluster components. Use the :ref:`upgrade
+- Upgrade all of the :program:`mongod` config server instances *one at
+  a time*. When you have *less* than *three* config servers active,
+  the cluster will be read-only which will prevent (and abort) all
+  chunk migrations and chunk splits.
+
+- Upgrade all remaining cluster components. Use the :ref:`upgrade
   procedure for replica sets <2.2-upgrade-replica-set>` for each of
   the shards and the :ref:`stand alone <2.2-upgrade-standalone>`
   procedure for each of the config servers. You may upgrade the