Abstract: A data storage device is provided. The data storage device includes: a flash memory, a dynamic random-access memory (DRAM), and a controller. The flash memory includes a plurality of physical blocks for storing data. The controller is configured to allocate a cache space from the DRAM according to at least one data feature of a write command from a host. The controller writes first data indicated by the write command into the cache space. In response to receiving a read command from the host, the controller determines whether the cache space contains all of the second data indicated by the read command. When the cache space contains all of the second data indicated by the read command, the controller retrieves the second data indicated by the read command directly from the cache space.