private void identifyOverRedundantBuckets() {
    overRedundancyBuckets = new TreeSet<>(REDUNDANCY_COMPARATOR);

    // For every bucket
    for (BucketRollup b : buckets) {
      if (b != null) {
        // check to see if the existing redundancy is greater than required
        if (b.getOnlineRedundancy() > requiredRedundancy) {
          // if so, add the bucket to the over redundancy list
          overRedundancyBuckets.add(b);
        } else {

          // figure out if we have over redundancy in a zone by having two members hosting a
          // bucket that should be spread across zones.
          determineOverRedundancyInZones(b);

        }
      }
    }
  }
Original functionality if bucket's redundancy is greater than what is necessary add it to the
over redundancy bucket list, so it can be cleared
<p>
Newly added functionality is to make this so that we don't have a bucket in the same redundancy
zone twice if zones are in use.
geode-core/src/main/java/org/apache/geode/internal/cache/partitioned/rebalance/model/PartitionedRegionLoadModel.java