def WriteTaskStart(self):
    """Writes task start information.

    Raises:
      IOError: if the storage type is not supported or
          when the storage writer is closed.
      OSError: if the storage type is not supported or
          when the storage writer is closed.
    """
    self._RaiseIfNotWritable()

    if self._storage_type != definitions.STORAGE_TYPE_TASK:
      raise IOError('Unsupported storage type.')

    task_start = self._task.CreateTaskStart()
    self._storage_file.WriteTaskStart(task_start)