-This backend supports all common storage properties, and adds an
-additional property called `path` to specify the directory. This
-needs to be an absolute file system path.
+This backend supports all common storage properties, and adds two
+additional properties. The `path` property is used to specify the
+directory. This needs to be an absolute file system path.
+
+The optional `content-dirs` property allows for the default layout
+to be changed. It consists of a comma-separated list of identifiers
+in the following format:
+
+ vtype=path
+
+Where `vtype` is one of the allowed content types for the storage, and
+`path` is a path relative to the mountpoint of the storage.