anchor.diff:  nest([],N,Acc) ->
       nest([],N-1,["0"|Acc]).
   
  +%% Borrowed from bitcask_fileops.erl and then mangled
  +-spec pack_ondisk(binary()) -> binary().
  +pack_ondisk(Bin) ->
  +    ValueSz = size(Bin),
  +    true = (ValueSz =< ?MAXVALSIZE),
  +    Bytes0 = [<<ValueSz:?VALSIZEFIELD>>, Bin],
  +    [<<(erlang:crc32(Bytes0)):?CRCSIZEFIELD>> | Bytes0].
  +
  +-spec unpack_ondisk(binary()) -> binary() | bad_crc.
  +unpack_ondisk(<<Crc32:?CRCSIZEFIELD/unsigned, Bytes/binary>>) ->
  +    case erlang:crc32(Bytes) of
  +        Crc32 ->
  +            <<ValueSz:?VALSIZEFIELD, Value:ValueSz/bytes>> = Bytes,
  +            Value;
  +        _BadCrc ->
  +            bad_crc
  +    end.
  +
   %%
   %% Test
   %%
  
positive.code: -spec start(integer(), config()) -> {ok, state()} | {error, term()}.
  start(Partition, Config) ->
      PartitionName = integer_to_list(Partition),
      ConfigRoot = app_helper:get_prop_or_env(fs_backend_data_root, Config, riak_kv),
      if
          ConfigRoot =:= undefined ->
              riak:stop("fs_backend_data_root unset, failing");
  
negative.code: %%       normal path.
  atomic_write(File, Val) ->
      FakeFile = File ++ ".tmpwrite",
      case file:write_file(FakeFile, pack_ondisk(Val)) of
          ok ->
              file:rename(FakeFile, File);
          X -> X
  