In a method for controlling data stored in an Solid State Disk (SSD) of a data de-duplication system, a storage controller obtains stability information of a data block. The stability information comprises a reference count of the data block and a length of a period of time when the data block is stored in the SSD. The storage controller identifies a stability level of the data block according to the stability information, and sends the stability level of the data block to the SSD. The SSD moves the data block to a target block which corresponds to the stability level. Thereby, the SSD can store data blocks having a same stability level together.