def METHOD_NAME(num_files, file_size):
    # TODO: We probably need to recreate these files each time.
    # Because you can specify --num-files and --large-file-size
    # those arguments can be potentially ignored if you've run
    # this previously with different values.
    many_files_dir = os.path.join(WORKDIR, MANY_FILES_DIR)
    if not os.path.exists(many_files_dir):
        os.makedirs(many_files_dir)
        run('caf gen --file-size 4kb --max-files %s --directory %s' %
            (num_files, many_files_dir))
    large_file_dir = os.path.join(WORKDIR, LARGE_FILE_DIR)
    if not os.path.exists(large_file_dir):
        os.makedirs(large_file_dir)
        run('caf gen --file-size %s --max-files 1 --directory %s' %
            (file_size, large_file_dir))