a first computer;

a first storage system coupled to said first computer;

a second storage system coupled to said first storage system; and

a second computer coupled to said second storage system,

wherein said first storage system includes a first controller and a plurality of first logical volumes accessed from said first controller,

wherein said second storage system includes a second controller and a plurality of second logical volumes accessed from said second controller,

wherein said plurality of first logical volumes include:

one or more primary data volumes which are primary logical volumes storing data to be referred to via said first controller by said first computer; and

a first command device which is a logical volume capable of storing a command for said first controller,

wherein said plurality of second logical volumes include:

each secondary data volume which is each secondary logical volume forming a pair with each primary data volume; and

a secondary command device, which is a logical volume capable of storing a command for said second controller,

wherein said primary command device is provided with a first management table for recording pair information to indicate which primary data volume and which secondary data volume form a pair,

wherein said second command device is provided with a second management table for recording pair information to indicate which primary data volume and which secondary data volume form a pair,

wherein said first controller stores command device management information regarding said first command device and said second command device forming a pair with said first command device,

wherein said first computer includes:

a first backup unit for controlling backup of data;

an access unit for reading data from said primary data volume and writing data to said primary data volume; and

a first copy control unit for controlling data copy from the primary data volume to the secondary data volume,

wherein said second computer includes:

a second backup unit for controlling backup of data; and

a second copy control unit for controlling data copy from the primary data volume to the secondary data volume,

wherein said first backup unit performs:

(a) staticizing said access unit so that said access unit does not write data to a certain primary data volume;

(b) preparing catalog information which is information including information on the time when said staticizing is performed, information on a pair of said certain primary data volume and said certain secondary data volume and information on said access unit; and

(c) sending instruction to write said prepared catalog information to said first management table and to copy the data in said certain primary data volume, to said first copy control unit,

wherein in response to the instruction, said first copy control unit writes a catalog write instruction to write said prepared catalog information in said first management table and a volume copy instruction to copy data in said certain primary data volume in a certain secondary data volume, to said first command device,

wherein said first controller, in response to said catalog write instruction stored in said first command device, writes said catalog information to said first management table,

wherein said first controller, in response to said volume copy instruction stored in said first command device, performs the following processes (A) and (B) concurrently:

(A) sending a write instruction which is an instruction to write catalog information written on said first management table and indicates said second command device recognized from said catalog command management information, to said second controller; and

(B) sending data groups from said certain primary data volume to said second controller,

wherein said second controller, in response to a write instruction from said first controller, writes catalog information to said second management table, writes the data group from said first controller to said certain secondary data volume,

wherein said second copy control unit receives said catalog information from said second management table and transfers said received catalog information to said second backup unit,

wherein said second backup unit, by using catalog information from said second copy control unit, performs backup or recovery of a data group in said certain secondary data volume,

wherein said catalog information is information for said second backup unit to perform backup or recovery, and is information for guaranteeing the consistency of the data used by said first backup unit.