private int getPartitionDefaultDiskWeight() {
    if (partitionDefaultDiskWeight.get() == 0) {
      ConfigAccessor configAccessor;
      if (clusterMapConfig.clusterMapUseAggregatedView) {
        configAccessor = helixAggregatedViewClusterInfo.helixManager.getConfigAccessor();
      } else {
        configAccessor =
            ((HelixDcInfo) dcToDcInfo.get(clusterMapConfig.clusterMapDatacenterName)).helixManager.getConfigAccessor();
      }
      logger.info("Fetching cluster config for {}", clusterName);
      ClusterConfig clusterConfig = configAccessor.getClusterConfig(clusterName);
      int defaultPartitionDiskWeight = clusterConfig.getDefaultPartitionWeightMap().get(DISK_KEY);
      logger.info("Default partition disk weight is {} for cluster {}", defaultPartitionDiskWeight, clusterName);
      partitionDefaultDiskWeight.compareAndSet(0, defaultPartitionDiskWeight);
    }
    return partitionDefaultDiskWeight.get();
  }
Return partition's default disk weight. It gets the weight from a local cache, if the weight is not present, it
will fetch it from cluster config.
@return
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixClusterManager.java