DOCS-15625-shards-must-be-replica-sets (#6566)

* DOCS-15625-shards-must-be-replica-sets

* Centralizing content and replacing with includes.

source/core/sharded-cluster-components.txt

@@ -16,21 +16,7 @@ Sharded Cluster Components
    :depth: 1
    :class: singlecol
 
-A MongoDB :term:`sharded cluster` consists of the following components:
-
-* :ref:`shard <shards-concepts>`: Each shard contains a
-  subset of the sharded data. As of MongoDB 3.6, shards must be deployed
-  as a :term:`replica set`.
-
-* :doc:`/core/sharded-cluster-query-router`: The ``mongos`` acts as a
-  query router, providing an interface between client applications and
-  the sharded cluster. Starting in MongoDB 4.4, :binary:`~bin.mongos`
-  can support :ref:`hedged reads <mongos-hedged-reads>` to minimize
-  latencies.
-
-* :ref:`config servers <sharding-config-server>`: Config
-  servers store metadata and configuration settings for the cluster. As
-  of MongoDB 3.4, config servers must be deployed as a replica set (CSRS).
+.. include:: /includes/fact-sharded-cluster-components.rst
 
 .. _sc-production-configuration:
 

source/includes/fact-sharded-cluster-components.rst

@@ -1,15 +1,15 @@
 A MongoDB :term:`sharded cluster` consists of the following components:
 
 - :ref:`shard <shards-concepts>`: Each shard contains a
-  subset of the sharded data. Each shard can be deployed as a :term:`replica
+  subset of the sharded data. Each shard must be deployed as a :term:`replica
   set`.
 
 - :doc:`/core/sharded-cluster-query-router`: The ``mongos`` acts as a
   query router, providing an interface between client applications and the
-  sharded cluster.
+  sharded cluster. Starting in MongoDB 4.4, :binary:`~bin.mongos`
+  can support :ref:`hedged reads <mongos-hedged-reads>` to minimize
+  latencies.
 
 - :ref:`config servers <sharding-config-server>`: Config
   servers store metadata and configuration settings for the cluster. As
   of MongoDB 3.4, config servers must be deployed as a replica set (CSRS).
-
-.. COMMENT TODO post code review, use this include file in /core/sharded-cluster-components.txt and /sharding.txt since they had duplicate content.

source/sharding.txt

@@ -81,19 +81,7 @@ MongoDB supports *horizontal scaling* through :term:`sharding`.
 Sharded Cluster
 ---------------
 
-A MongoDB :term:`sharded cluster` consists of the following components:
-
-* :ref:`shard <shards-concepts>`: Each shard contains a
-  subset of the sharded data. Each shard can be deployed as a :term:`replica
-  set`.
-
-* :doc:`/core/sharded-cluster-query-router`: The ``mongos`` acts as a
-  query router, providing an interface between client applications and
-  the sharded cluster. Starting in MongoDB 4.4, ``mongos`` can support
-  :ref:`hedged reads <mongos-hedged-reads>` to minimize latencies.
-
-* :ref:`config servers <sharding-config-server>`: Config
-  servers store metadata and configuration settings for the cluster.
+.. include:: /includes/fact-sharded-cluster-components.rst
 
 The following graphic describes the interaction of components within a
 sharded cluster:

source/tutorial/troubleshoot-sharded-clusters.txt

@@ -128,7 +128,7 @@ To ensure cluster availability:
 Config Database String Error
 ----------------------------
 
-Config servers can be deployed as replica
+Config servers must be deployed as replica
 sets. The :binary:`~bin.mongos` instances for the sharded cluster must
 specify the same config server replica set name but can specify
 hostname and port of different members of the replica set.