public static ConfigDiskService getInstance() {
        if (configDiskService == null) {
            synchronized (ConfigDiskServiceFactory.class) {
                if (configDiskService == null) {
                    String type = System.getProperty("config_disk_type", TYPE_RAW_DISK);
                    if (type.equalsIgnoreCase(TYPE_ROCKSDB)) {
                        configDiskService = new ConfigRocksDbDiskService();
                    } else {
                        configDiskService = new ConfigRawDiskService();
                    }
                }
                return configDiskService;
            }
        }
        return configDiskService;
    }
@Test
    void getRawDiskInstance() {
        System.setProperty("config_disk_type", "rawdisk");
        ConfigDiskService instance = ConfigDiskServiceFactory.getInstance();
        assertTrue(instance instanceof ConfigRawDiskService);
    }