1. A method comprising: in a data storage device that includes a non-volatile memory and a controller coupled to the non-volatile memory, the controller including a bus and a processor coupled to the bus, wherein the data storage device further includes a volatile memory having a first interface and a resistive random access memory (ReRAM) having a second interface, wherein the controller is configured to store user data at the non-volatile memory via a controller-to-non-volatile memory interface, performing: accessing the volatile memory via the first interface, wherein the volatile memory is coupled to the bus via the first interface; storing data at the ReRAM via the second interface prior to a low-power event; and retrieving the data from the ReRAM via the second interface after a power restoration event, wherein the ReRAM is coupled to the bus via the second interface.