DOCS-13889 display freeStorageSize limit

Author: mungitoperrito

source/reference/command/dbStats.txt

@@ -151,6 +151,8 @@ Output
    allocated to indexes. See :data:`~dbStats.indexFreeStorageSize` for
    the total free index size.
 
+   This value is always included in the :dbcommand:`dbStats` output.
+
    .. versionadded:: 5.0
 
 .. data:: dbStats.indexes
@@ -219,4 +221,15 @@ Output
    Total size of all disk capacity on the filesystem where MongoDB
    stores data.
 
-   .. versionadded:: 3.6
+Examples
+--------
+
+If you are only interested in one field, the output of the
+:dbcommand:`dbStats` command can be limited to just that field. For
+example, the following command returns the current total free
+storage size.
+
+.. code-block:: javascript
+
+   db.runCommand( { dbStats: 1 } ).freeStorageSize
+   

source/reference/method/db.stats.txt

@@ -62,23 +62,25 @@ the database system's state. For example:
 .. code-block:: javascript
 
    {
-      "db" : "test",
-      "collections" : 6,
-      "views" : 0,
-      "objects" : 400629,
-      "avgObjSize" : 663.996695196803,
-      "dataSize" : 266016332,
-      "storageSize" : 179838976,
-      "indexes" : 13,
-      "indexSize" : 9940992,
-      "totalSize" : 189779968,
-      "scaleFactor" : 1,
-      "fsUsedSize" : 126727540736,
-      "fsTotalSize" : 499963174912,
-      "ok" : 1
+	   "db" : "admin",
+	   "collections" : 2,
+	   "views" : 0,
+	   "objects" : 5,
+	   "avgObjSize" : 336.8,
+	   "dataSize" : 1684,
+	   "storageSize" : 69632,
+	   "freeStorageSize" : 28672,
+	   "indexes" : 3,
+	   "indexSize" : 106496,
+	   "indexFreeStorageSize" : 45056,
+	   "totalSize" : 176128,
+	   "totalFreeStorageSize" : 73728,
+	   "scaleFactor" : 1,
+	   "fsUsedSize" : 47881682944,
+	   "fsTotalSize" : 62725623808,
+	   "ok" : 1
    }
 
-
 For an explanation of the
 output, see :ref:`dbstats-output`.
 
@@ -112,3 +114,20 @@ The following example returns various size values in kilobytes:
 .. note::
 
    The scale factor rounds values to whole numbers.
+
+You can also use ``db.stats()`` to return a single value, such as the
+``freeStorageSize``.
+
+.. code-block:: javascript
+
+   db.stats().freeStorageSize
+   db.stats(1024).freeStorageSize
+
+The output shows the difference between the raw and scaled values.
+
+.. code-block:: javascript
+   :copyable: false
+
+   28672
+   28
+