 The controller essentially "lies" to the operating system and reports that the writes have been completed in order (a lie that improves performance at the expense of data corruption if power is lost), and the battery backup hedges against the risk of data corruption by giving the controller a way to silently fix any and all damage that could occur as a result.If the power gets shut off after element 4 has been written, the battery backed memory contains the record of commitment for the other three items and ensures that they are written ("flushed") to the disk at the next available opportunity.Consistency (database systems) in the realm of Distributed database systems refers to the property of many ACID databases to ensure that the results of a Database transaction are visible to all nodes simultaneously.