anchor.diff:          %% LUMA API Key, must be identical with API Key in external LUMA
           %% service.
           lumaApiKey => {string, optional},
  -        %% The type of storage.
  -        type => {equal, <<"glusterfs">>},
           %% The name of the volume to use as a storage backend.
           volume => string,
           %% The hostname (IP address or FQDN) of GlusterFS volume server.
  
positive.code: -spec glusterfs_model() -> maps:map().
  glusterfs_model() ->
      #{
          %% The Id of storage.
          id => {string, optional},
          %% The name of storage.
  
negative.code: -spec posix_model() -> maps:map().
  posix_model() ->
      #{
          %% The type of storage.
          type => {equal, <<"posix">>},
          %% The Id of storage.
          id => {string, optional},
          %% The name of storage.
  