According to on embodiment, a memory system includes a non-volatile memory, a memory controller including a data buffer configured to store first data, and a backup power supply configured to supply first power to the non-volatile memory and the memory controller, when second power from an external main power supply is off. The memory controller is configured to write second data including information identifying the first data in the non-volatile memory without writing the first data in the non-volatile memory, when the first power is supplied from the backup power supply, and transmit the information stored in the non-volatile memory to an external host device, after a recovery of the second power from the main power supply.