Storage system and method for controlling storage system

A method for controlling a storage system including a plurality of control devices, the plurality of control devices each including an interface unit and an arithmetic processing unit, the method comprising:

• receiving, by a first interface unit, an instruction regarding output or input of data to or from a storage device, the first interface unit being included in a first control device out of the plurality of control devices;
• receiving, by a first arithmetic processing unit, the instruction from the first interface unit and executing the instruction, the first arithmetic processing unit being included in the first control device;
• selecting by the first arithmetic processing unit, when an error has occurred in a specific interface unit, a first processing unit and requesting the first processing unit to execute saving processing for saving dump data of the specific interface unit, the specific interface unit being included in one of the plurality of control devices, the first processing unit being included in one of the plurality of control devices, and
• selecting by the first arithmetic processing unit, when a usage rate of the first processing unit goes beyond a threshold range during execution of the saving processing, a second processing unit and requesting the second processing unit to execute the saving processing, the second processing unit being included in one of the plurality of control devices.