Hi guys ,
just want to share my knowledge of understanding the important role played by Persistance Storage.
The Main Advantage of Persistance Storage is to get back the data in case of Power Failure or any kind of unexpected chaos.
During Normal Operation of the Database, Data is automatically saved from memory to SSD(solid state drives) at regular save points. all data changes are captures in logs aswell. the logs are saved from memory to disks after each database transaction committed.
Incase of power failure,the database can be started like any traditional disk-base database and can retrive the data from the last consistent state by replaying the log since the last savepoint.
this is my simple understanding about the Persistance Storage,hope it helps.