If the pair state of a certain volume pair in one copy group is a fault state which has changed due to occurrence of a fault in the volume pair, then a write holding state is set for the copy group, and after setting the write holding state, the pair states of all the other volume pairs belonging to the copy group are set to a copy halt state. When setting the write holding state, and when executing setting of the copy halt setting state, commands from an open host are not necessary.