Ceph

crush-map.rst claims that the bucket type defaults are as appear in the table, but they're
not defaults; they must be explicitly specified in the file. Also, how to specify them
is not documented.

CRUSH Map Buckets
-----------------

CRUSH maps support the notion of 'buckets', which may be thought of as nodes
that aggregate other buckets into a hierarchy of physical locations, where OSD
devices are the leaves of the hierarchy. The following table lists the default
types.

+------+----------+-------------------------------------------------------+
| Type | Location    | Description                                        |
+======+=============+====================================================+
|  0   |   OSD       | An OSD daemon (e.g., osd.1, osd.2, etc).           |
+------+-------------+----------------------------------------------------+
|  1   |   Host      | A host name containing one or more OSDs.           |
+------+-------------+----------------------------------------------------+
|  2   |   Rack      | A computer rack. The default is ``unknownrack``.   |
+------+-------------+----------------------------------------------------+
|  3   |   Row       | A row in a series of racks.                        |
+------+-------------+----------------------------------------------------+
|  4   |   Room      | A room containing racks and rows of hosts.         |
+------+-------------+----------------------------------------------------+
|  5   | Data Center | A physical data center containing rooms.           |
+------+-------------+----------------------------------------------------+
|  6   |   Pool      | A data storage pool for storing objects.           |
+------+-------------+----------------------------------------------------+

.. tip:: You can remove these types and create your own bucket types.