Cast the disk stats to float and convert them to bytes

def _format_disk_metrics(self, metrics):
        """Cast the disk stats to float and convert them to bytes"""
        for name, raw_val in metrics.iteritems():
            if raw_val:
                match = DISK_STATS_RE.search(raw_val)
                if match is None or len(match.groups()) != 2:
                    self.log.warning('Can\'t parse value %s for disk metric %s. Dropping it.' % (raw_val, name))
                    metrics[name] = None
                val, unit = match.groups()
                # by default some are uppercased others lowercased. That's error prone.
                unit = unit.lower()
                try:
                    val = int(float(val) * UNIT_MAP[unit])
                    metrics[name] = val
                except KeyError:
                    self.log.error('Unrecognized unit %s for disk metric %s. Dropping it.' % (unit, name))
                    metrics[name] = None
        return metrics