1. A memory device, comprising: a first storage unit storing an address mapping table; a control unit coupled to the first storage unit and including a second storage unit storing a risky mapping table and a cached mapping table, wherein the risky mapping table stores mapping information of risky data, the risky data being data that can be damaged by power interruption; wherein the control unit is configured to: write data into the first storage unit; update mapping information associated with the data in the risky mapping table; when the data has been written into an upper page in a set of paired pages in the first storage unit, commit mapping information that is in the risky mapping table and that is associated with the data into the cached mapping table; and store mapping information in the cached mapping table into the address mapping table.