anchor.diff:      NewServers = DeltaNodes ++ Servers,
   
       misc:update_proplist(BucketConfig, [{map, TransitionalMap},
  -                                        {servers, NewServers}]).
  +                                        {servers, NewServers},
  +                                        {deltaRecoveryMap, {TargetMap, Options}}]).
   
   get_delta_recovery_nodes(Config, Nodes) ->
       [N || N <- Nodes,
  
positive.code:             do_wait_for_bucket(Bucket, Zombies)
      end.
  
  build_transitional_bucket_config(BucketConfig, TargetMap, DeltaNodes) ->
      {num_replicas, NumReplicas} = lists:keyfind(num_replicas, 1, BucketConfig),
      {map, CurrentMap} = lists:keyfind(map, 1, BucketConfig),
      {servers, Servers} = lists:keyfind(servers, 1, BucketConfig),
  
negative.code: 
  generate_vbucket_map(CurrentMap, KeepNodes, BucketConfig) ->
      Opts = generate_vbucket_map_options(KeepNodes, BucketConfig),
  
      Map0 =
          case lists:keyfind(deltaRecoveryMap, 1, BucketConfig) of
              {deltaRecoveryMap, DRMapAndOpts} when DRMapAndOpts =/= undefined ->
                  {DRMap, _} = DRMapAndOpts,
                  MatchingMaps =
                      mb_map:find_matching_past_maps(KeepNodes, CurrentMap, Opts,
                                                     [DRMapAndOpts]),
                  case lists:member(DRMap, MatchingMaps) of
                      true ->
                          DRMap;
                      false ->
                          undefined
                  end;
              _ ->
                  undefined
          end,
  
      Map = case Map0 of
                undefined ->
                    EffectiveOpts = [{maps_history, ns_bucket:past_vbucket_maps()} | Opts],
                    mb_map:generate_map(CurrentMap, KeepNodes, EffectiveOpts);
                _ ->
                    Map0
            end,
  
      {Map, Opts}.
  
  generate_initial_map(BucketConfig) ->
      Chain = lists:duplicate(proplists:get_value(num_replicas, BucketConfig) + 1,
  