int getHostTotalDiskCapacityUsage() {
    AmbryDataNode dataNode = instanceNameToAmbryDataNode.get(selfInstanceName);
    String dcName = dataNode.getDatacenterName();
    for (String tag : instanceNameToInstanceConfig.get(selfInstanceName).getTags()) {
      // Call this method to make sure the partition weight map is populated
      getResourceConfig(dcToTagToResourceProperty.get(dcName).get(tag).name, clusterMapConfig.clusterMapDatacenterName);
    }
    Map<String, AmbryReplica> replicas = ambryDataNodeToAmbryReplicas.get(dataNode);
    return replicas.keySet().stream().mapToInt(this::getPartitionDiskWeight).sum();
  }
Callback method when this data node is becoming SEMI AUTO from FULL AUTO.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixClusterManager.java