Provided is a controller in a computer system, the computer system including a plurality of data storage systems, and at least one controller for controlling access to data stored in the plurality of data storage systems, the each controller including: an interface coupled to the network; a processor coupled to the interface; and a storage unit coupled to the processor, in which: the storage unit holds attribute information indicating whether to permit access to the data; and the processor is configured to: receive a writing request of the data from a client computer coupled to the network; judge whether each of the each controller permits the requested writing based on the held attribute information and information of a location where the each controller is installed; and write the data in a data storage system controlled by a controller judged to permit the writing.