A data storage system is a data storage system which is mounted on a moving body. The data storage system includes: a plurality of ECUs which are connected to a network in the moving body; a shared storage device into which data is writable by each of the plurality of ECUs; and a shared priority controller which is connected between the plurality of ECUs and the shared storage device, and controls an order of priority in which data is written into the shared storage device from each of the plurality of ECUs.