A method for managing data stored in a hierarchical storage unit of a storage apparatus is disclosed. The storage unit includes a first storage medium having a first access speed and a second storage medium having a second access speed. The first access speed is different from the second access speed. The method comprises determining a first access frequency for information of first type, the first access frequency being associated with a first period of past time. A second access frequency of the information of first type is determined. The second access frequency is associated with a second period of past time and is different than the first access frequency. At least a portion of the information of first type is transferred from the first storage medium to the second storage medium prior to a second period based on the second access frequency determined in the determining-a-second-access-frequency step, the second period corresponding to the second period of past time.