/**
  * Return the filling percentage of the backend storage
  *
  * @return int integer between 0 and 100
  */
 public function getFillingPercentage()
 {
     $result = $this->_database->execute('db.stats()');
     $total = @$result['retval']['storageSize'] ?: 0;
     $free = $total - @$result['retval']['dataSize'] ?: 0;
     if ($total == 0) {
         Zend_Cache::throwException('can\'t get disk_total_space');
     } else {
         if ($free >= $total) {
             return 100;
         }
         return (int) (100.0 * ($total - $free) / $total);
     }
 }