anchor.diff:  When working with the MongoDB backend, you can specify the following settings:
   
   * the write concern for entities and associations using the +@WriteConcern+ annotation
  +* the read preference for entities and associations using the +@ReadPreference+ annotation
   * a strategy for storing associations using the +@AssociationStorage+ and +@AssociationDocumentStorage+ annotations
   (refer to <<ogm-mongodb-storage-prinicples>> to learn more about these options).
   
  
positive.code: When working with MongoDB, you can currently configure the following options using the API:
  
  * write concern
  * association storage strategy
  * association document storage strategy
  
  
negative.code: This is useful in cases where the pre-defined configurations are not sufficient,
  e.g. if you want to ensure that writes are propagated to a specific number of replicas or given "tag set".
  Only takes effect if +hibernate.ogm.mongodb.write_concern+ is set to +CUSTOM+.
  hibernate.ogm.mongodb.read_preference::
  Specifies the +ReadPreference+ to be applied when issuing reads against the MongoDB datastore.
  Possible settings are (values of the +ReadPreferenceType+ enum):
  +PRIMARY+, +PRIMARY_PREFERRED+, +SECONDARY+, +SECONDARY_PREFERRED+ and +NEAREST+.
  It's currently not possible to plug in custom read preference types.
  If you're interested in such a feature, please let us know.
  
  For more information, please refer to the
  http://api.mongodb.org/java/current/com/mongodb/WriteConcern.html[official documentation].
  