DOCS-20573 arbiters write concern (#482) (#552)

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

* DOCSP-20573-arbiters-write-concern

Co-authored-by: jason-price-mongodb <[email protected]>

Co-authored-by: jason-price-mongodb <[email protected]>

Author: jason-price-mongodb

source/includes/admonition-multiple-arbiters.rst

@@ -1,6 +1,21 @@
 .. warning:: 
 
-   Avoid deploying more than one arbiter per replica set.
+   Avoid deploying more than one :term:`arbiter` in a :term:`replica
+   set`. See :ref:`rollbacks-multi-arbiters`.
 
-   See also: :ref:`rollbacks-multi-arbiters`
+To add an arbiter to an existing replica set:
 
+- Typically, if there are two or fewer data-bearing members in the
+  replica set, you might need to first set the :ref:`cluster wide write
+  concern <set_global_default_write_concern>` for the replica set.
+
+- See :ref:`cluster wide write concern
+  <set_global_default_write_concern>` for more information on why you
+  might need to set the cluster wide write concern.
+
+You do not need to change the cluster wide write concern before starting
+a new replica set with an arbiter.
+
+.. seealso::
+
+   :ref:`Default write concern formula <default-wc-formula>`

source/reference/write-concern.txt

@@ -468,6 +468,8 @@ For example, consider:
      topology that does not require all data bearing voting members to be
      available (e.g. P-S-S).
 
+.. include:: /includes/admonition-multiple-arbiters.rst
+
 Write Concern Provenance
 ~~~~~~~~~~~~~~~~~~~~~~~~