private static void initSystemMetrics(MetricService metricService) {
    ArrayList<String> diskDirs = new ArrayList<>();
    diskDirs.add(IoTDBDescriptor.getInstance().getConfig().getSystemDir());
    diskDirs.add(IoTDBDescriptor.getInstance().getConfig().getConsensusDir());
    diskDirs.addAll(Arrays.asList(IoTDBDescriptor.getInstance().getConfig().getDataDirs()));
    diskDirs.addAll(Arrays.asList(CommonDescriptor.getInstance().getConfig().getWalDirs()));
    diskDirs.add(CommonDescriptor.getInstance().getConfig().getSyncDir());
    diskDirs.add(IoTDBDescriptor.getInstance().getConfig().getSortTmpDir());
    SystemMetrics.getInstance().setDiskDirs(diskDirs);
    metricService.addMetricSet(SystemMetrics.getInstance());
  }
Bind predefined metric sets into DataNode.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/service/metrics/DataNodeMetricsHelper.java