docs: def _add_mdisk(self, userid, disk, vdev):
          """Create one disk for userid
  
          NOTE: No read, write and multi password specified, and
          access mode default as 'MR'.
  
          """
          size = disk['size']
          fmt = disk.get('format', 'ext4')
          disk_pool = disk.get('disk_pool') or CONF.zvm.disk_pool
          [diskpool_type, diskpool_name] = disk_pool.split(':')
  
          if (diskpool_type.upper() == 'ECKD'):
              action = 'add3390'
          else:
              action = 'add9336'
  
          rd = ' '.join(['changevm', userid, action, diskpool_name,
                         vdev, size, '--mode MR'])
          if fmt and fmt != 'none':
              rd += (' --filesystem %s' % fmt.lower())
  
          action = "add mdisk to userid '%s'" % userid
          with zvmutils.log_and_reraise_smt_request_failed(action):
              self._request(rd)