code: function format(data) {
      const time = util.formatTime(new Date());
      const outputArray = data.toString().replace(/^\s+|\s+$/g, '').split(/\s+/);
      const outputValues = [];
      for (let i = 0, counter = 0; i < outputArray.length; i++) {
          if (!isNaN(outputArray[i])) {
              outputValues[counter] = parseFloat(outputArray[i]);
              counter++;
          }
      }
      if (outputValues.length > 0) {
          return {
              date: time,
              disk: {
                  kb_read: outputValues[9],
                  kb_wrtn: outputValues[10],
                  kb_read_per: outputValues[7],
                  kb_wrtn_per: outputValues[8],
                  tps: outputValues[6]
              },
              cpu: {
                  cpu_user: outputValues[0],
                  cpu_nice: outputValues[1],
                  cpu_system: outputValues[2],
                  cpu_iowait: outputValues[3],
                  cpu_steal: outputValues[4],
                  cpu_idle: outputValues[5]
              }
          };
      }
      return false;
  }
docs: analysis the disk i/o data,return a map contains kb_read,kb_wrtn ect.
  
  @param {String} data, the output of the command 'iostat'
  @api private