anchor.diff:                          ResidenceCalculator),
       PendingResRate = Z2(vb_pending_num_non_resident, vb_pending_curr_items,
                           ResidenceCalculator),
  +
  +    AverageWriteSeekDistance = Z2(write_seeks_distance, write_seeks_count,
  +                                  fun (Distance, Count) ->
  +                                          try Distance / Count
  +                                          catch error:badarith -> 0
  +                                          end
  +                                  end),
  +
       [{hit_ratio, HitRatio},
        {ep_cache_miss_rate, EPCacheMissRatio},
        {ep_resident_items_rate, ResidentItemsRatio},
  
positive.code:                           {desc, <<"High water mark for auto-evictions (measured from ep_mem_high_wat)">>}]},
                  {struct, [{title, <<"low water mark">>},
                            {name, <<"ep_mem_low_wat">>},
                            {desc, <<"Low water mark for auto-evictions (measured from ep_mem_low_wat)">>}]}
               ]}]},
       {struct,[{blockName,<<"vBucket Resources">>},
                {extraCSSClasses,<<"withtotal closed">>},
  
negative.code:      {vb_avg_total_queue_age, AvgTotalQueueAge},
       {vb_active_resident_items_ratio, ActiveResRate},
       {vb_replica_resident_items_ratio, ReplicaResRate},
       {vb_pending_resident_items_ratio, PendingResRate},
       {avg_write_seek_distance, AverageWriteSeekDistance}].
  
  %% converts list of samples to proplist of stat values.
  %%
  