// Create top level directories if they don't exist.
	// with mode 0o777 mkdir honors system umask.
	mkdirAll(pathutil.Dir(filePath), 0o777, s.drivePath) // don't need to fail here

	w, err := s.openFileDirect(filePath, os.O_CREATE|os.O_WRONLY|os.O_EXCL)
	if err != nil {
		return err
	}
	_, err = w.Write(alignedBuf)
	w.Close()
	if err != nil {
		if isSysErrInvalidArg(err) {
			err = errUnsupportedDisk