anchor.diff:      ExternalFileId = <<"external_file_id">>,
   
       % create test file
  -    {ok, FileUuid} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
  -    {ok, Handle} = lfm_proxy:open(W1, SessionId, {uuid, FileUuid}, rdwr),
  +    {ok, FileGUID} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
  +    FileUuid = fslogic_uuid:file_guid_to_uuid(FileGUID),
  +    {ok, Handle} = lfm_proxy:open(W1, SessionId, {guid, FileGUID}, rdwr),
       ?assertMatch({ok, 10}, lfm_proxy:write(W1, Handle, 0, <<"0123456789">>)),
       ?assertMatch(ok, lfm_proxy:fsync(W1, Handle)),
   
  
positive.code:     [W1 | _] = ?config(op_worker_nodes, Config),
      ProviderId = initializer:domain_to_provider_id(?GET_DOMAIN(W1)),
      SessionId = <<"session_id1">>,
      {ok, FileUuid} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
      {ok, Handle} = lfm_proxy:open(W1, SessionId, {uuid, FileUuid}, rdwr),
  
      %when
      ?assertMatch({ok, 2}, lfm_proxy:write(W1, Handle, 0, <<"01">>)),
  
negative.code:     ExternalFileId = <<"external_file_id">>,
  
      % create test file
      {ok, FileGUID} = lfm_proxy:create(W1, SessionId, <<"test_file">>, 8#777),
      FileUuid = fslogic_uuid:file_guid_to_uuid(FileGUID),
      {ok, Handle} = lfm_proxy:open(W1, SessionId, {guid, FileGUID}, rdwr),
      ?assertMatch({ok, 10}, lfm_proxy:write(W1, Handle, 0, <<"0123456789">>)),
      ?assertMatch(ok, lfm_proxy:fsync(W1, Handle)),
  
  