public function getStorage()
    {
        if (! $this->storage) {
            if (! $this->hasOption(self::OPTION_PERSISTENCE)) {
                throw new InconsistencyConfigException(__('Maintenance service must have a persistence option.'));
            }
            $this->storage = new MaintenanceStorage(
                \common_persistence_Manager::getPersistence($this->getOption(self::OPTION_PERSISTENCE))
            );
        }
        return $this->storage;
    }