Apparatus and method for secure data disposal

When data is stored for a certain retention period, well prior to the expiration date, the storage controller starts encryption of data on a certain volume while ensuring data access from hosts, and repeats read and write of the data predefined number of times while also ensuring data access from hosts. When the expiration date is reached and if the encryption completes, the storage controller dispose of the encryption keys. Using this technique, one can reuse the volume for other purposes as soon as the expiration is reached. Because one can start this process even much earlier than the expiration date, one can balance the workload of the controller by scheduling the process in order to avoid the peak of the workload for the data disposal process. Also, it is possible to minimize the period to manage encryption keys which makes key management easier.