A data processing method and device, and a distributed storage system are described. The method and device are applied in a dual-control storage server. The dual-control storage server comprises two controllers. If one controller fails due to abnormalities, the other controller determines the storage device managed by the failed controller, and the other controller scans the data in the determined storage device to obtain the metadata of the storage device, and uses the metadata to read the data stored in the determined storage device. It can be seen that in this solution, if one controller is abnormal, the other controller will take the place of the failed controller to provide external services. This improves the stability of the data storage by the dual-control storage server.