anchor.diff:  
   generate_vbucket_map(CurrentMap, KeepNodes, BucketConfig) ->
       Opts = generate_vbucket_map_options(KeepNodes, BucketConfig),
  -    EffectiveOpts = [{maps_history, ns_bucket:past_vbucket_maps()} | Opts],
  -
  -    {mb_map:generate_map(CurrentMap, KeepNodes, EffectiveOpts), Opts}.
  +
  +    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,
  
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:                                                 KeepNodes, BucketCompletion,
                                                  NumBuckets, DeltaRecoveryBuckets),
                                    ns_bucket:set_map_opts(BucketName, MapOptions),
                                    ns_bucket:update_bucket_props(BucketName,
                                                                  [{deltaRecoveryMap, undefined}]),
                                    master_activity_events:note_bucket_rebalance_ended(BucketName),
                                    verify_replication(BucketName, KeepNodes, NewMap)
                            end
  