1. A persistent storage device, comprising: persistent storage, comprising a set of persistent storage blocks; NVRAM, comprising a type of nonvolatile storage distinct from the persistent storage and comprising a set of NVRAM blocks; a storage controller configured to receive commands from an external host device in accordance with one or more applications executed by the external host device, and further configured to: in response to a host NVRAM write command received from the external host device, store data to an NVRAM block specified by the host NVRAM write command; in response to a host NVRAM read command received from the external host device, retrieve data from an NVRAM block specified by the host NVRAM read command; and in response to a transfer command received from the external host device, transfer data in an NVRAM block specified by the transfer command to a corresponding persistent storage block, wherein the data was previously written to the specified NVRAM block.