public function setBackupPath($filePath)
    {
        $path = realpath(dirname($filePath));
        if (!is_dir($path)) {
            throw new FilesystemException(sprintf(
                'The backup directory does not exist: %s.', $path
            ));
        }
        if (!is_writable($path)) {
            throw new FilesystemException(sprintf(
                'The backup directory is not writeable: %s.', $path
            ));
        }
        $this->backupPath = $filePath;
    }