Identify the missing word(s) in the following sentence within the context of Microsoft Azure. Azure Database for MySQL has a service level agreement, which guarantees availability of 99.99%, meaning nearly no downtime should be encountered. For Azure Database for MySQL, if a node-level problem happens such as hardware failure, a built-in failover mechanism will kick in. All transactional changes to the MySQL database are written [?] to storage upon commit. If a node-level interruption occurs, the database server automatically creates a new node and attaches the data storage.