getLocalThumbnailPath() will create too large of media-youtube/ folder on high traffic sites

Problem/Motivation

The function getLocalThumbnailPath() in MediaYouTubeStreamWrapper.inc copies thumbnails to a single directory. This is a scaling problem on high traffic sites with many video thumbnails, as the directory can become too large. This can hinder site performance with folders with large amounts of files (~2,500). Breaking the folder into small sub-folders fixes the issue.

function getLocalThumbnailPath() {
    $parts = $this->get_parameters();
    $local_path = file_default_scheme() . '://media-youtube/' . check_plain($parts['v']) . '.jpg';

    if (!file_exists($local_path)) {
      // getOriginalThumbnailPath throws an exception if there are any errors
      // when retrieving the original thumbnail from YouTube.
      try {
        $dirname = drupal_dirname($local_path);
        file_prepare_directory($dirname, FILE_CREATE_DIRECTORY | FILE_MODIFY_PERMISSIONS);
        $response = drupal_http_request($this->getOriginalThumbnailPath());

        if (!isset($response->error)) {
          file_unmanaged_save_data($response->data, $local_path, TRUE);
        }
        else {
          @copy($this->getOriginalThumbnailPath(), $local_path);
        }
      }
      catch (Exception $e) {
        // In the event of an endpoint error, use the mime type icon provided
        // by the Media module.
        $file = file_uri_to_object($this->uri);
        $icon_dir = variable_get('media_icon_base_directory', 'public://media-icons') . '/' . variable_get('media_icon_set', 'default');
        $local_path = file_icon_path($file, $icon_dir);
      }
    }

    return $local_path;
  }
}

Proposed resolution

Change the $local_path to include an additional folder structure to breakup the directory into smaller sub-folders. Perhaps adding date information (Y/m/d) or video id ($parts['v']). This will prevent a single folder from getting too large.

Also the function media_youtube_cache_clear($fids) will need changed to support recursive deletion by changing line 40 to file_unmanaged_delete_recursive($local_path).