Computer system, management method and storage network system

A computer system comprising:

• a first storage system coupled to a primary host computer;
• a second storage system coupled to a secondary host computer;
• a third storage system;
• wherein said first storage system is coupled to said second storage system and said third storage system, and said second storage system is coupled to said third storage system,
• wherein, when a state of said primary host computer is in an active state, a data sent from the primary host computer to said first storage system is copied through a first copy route which includes a route from said first storage system to said second storage system and a route from said second storage system to said third storage system,
• wherein, if a failure occurs in said primary host computer and a state of said second host computer is to be in an active state, a data sent from said secondary host computer to said second storage system is copied through a second copy route which includes a route from said second storage system to said first storage system and a route from said first storage system to said third storage system.