A method, system, and computer-usable medium for operating a mobile computer system. In response to receiving a write request, a control system attempts to write data associated with said write request to a non-volatile memory cache coupled to said hard disk drive. In response to determining the non-volatile memory cache cannot accommodate the data, the control system starts the hard disk drive. The control system writes contents of the non-volatile memory cache to the hard disk drive, after starting the hard disk drive. In response to determining the non-volatile memory cache can accommodate said data, the control system writes the data to the non-volatile memory cache.