1. An in-line persistent storage device comprising: a housing adapted to be connected to a disk drive connector of a disk drive; an array of solid state, non-volatile (“NV”) memory blocks mounted within the housing and in communication with the disk drive and a controller, the controller in communication with the disk drive, the controller for controlling the NV memory and adapted to store at least one data block received from a computing device in at least one memory block in NV memory and flush the at least one block of data in response to receiving a flush command, the array of solid state NV memory blocks.