1. A non-volatile mass storage device comprising: memory circuitry accessible to a host data processing device via a communication link; processing circuitry for locally accessing said memory circuitry as a file system and for generating a file for storage on said memory circuitry; wherein said processing circuitry is triggered to generate said file by connection of said non-volatile mass storage device to said host data processing device and said file comprises information dependent upon a state of said non-volatile mass storage device.