def quota(cls, id):
        """return disk quota used/free"""
        sampler = {'unit': 'minutes', 'value': 1, 'function': 'avg'}
        query = 'vfs.df.bytes.all'
        metrics = Metric.query(id, 60, query, 'paas', sampler)

        df = {'free': 0, 'used': 0}
        for metric in metrics:
            what = metric['size'].pop()
            # we need the most recent points
            metric['points'].reverse()
            for point in metric['points']:
                if 'value' in point:
                    df[what] = point['value']
                    break
        return df
return disk quota used/free