The present disclosure relates to an apparatus for a data storage device, an adapter, an array controller, a data storage device, and a relevant method. The apparatus for the data storage device comprises: a power management module configured to detect power-off of a power supply and to switch to a backup battery unit in the data storage device in response to detecting the power supply. The apparatus is configured to cause the backup battery unit to supply power only to the volatile memory in the data storage device. By using a solution according to the present disclosure, for example, preserving time for data may be prolonged in the case of power-off.