Network system and its switches

A network system comprising:

• a computer;
• a switch that is connected to said computer via a network;
• a first storage device that is connected to said switch via the network;
• and
• a second storage device that is connected to said switch via the network;
• wherein said switch beforehand transfers data stored in said first storage device to said second storage device;
• said switch provides said computer with a third storage device corresponding to said first storage device, said third storage device being a virtual storage;
• said computer issues a data read request to said third storage device;
• when receiving said data read request, said switch converts the data read request to said third storage device into a data read request to said second storage device, and then transmits the converted data read request to said second storage device;
• when receiving said data read request, said second storage device transfers, to said switch, data corresponding to the received data read request;
• and
• when receiving the data, said switch transfers the received data to said computer as data transferred from said third storage device.

A network system comprising:

• a computer;
• a first storage device that is connected to said computer via a network;
• and
• a second storage device that is connected to said computer via the network;
• wherein said second storage device comprises a switch unit that is connected to said computer and said first storage device via the network, and a storage unit that is connected to said switch unit via an internal network;
• said switch unit beforehand transfers data stored in said first storage device to said storage unit;
• said computer issues a read request for the data stored in said first storage device;
• when receiving said read request, said switch unit converts the read request for the data stored in said first storage device into a data read request to said storage unit, and then transmits the converted data read request to said storage unit;
• when receiving said data read request, said storage unit transfers, to said switch unit, data corresponding to the received data read request;
• and
• when receiving the data, said switch unit transfers the received data to said computer as data transferred from said first storage device.

A network system comprising:

• a computer;
• a switch that is connected to said computer via a network;
• a first storage device that is connected to said switch via the network;
• and
• a second storage device that is connected to said switch via the network;
• wherein said computer issues a read request for the data stored in said first storage device;
• when said switch receives said read request, if the data stored in said first storage device is stored in said second storage device, said switch converts said read request for the data stored in said first storage device into a data read request to said second storage device, and then transmits the converted data read request to said second storage device, whereas if the data stored in said first storage device is not stored in said second storage device, said switch transmits said read request to said first storage device without converting said read request for the data;
• when receiving said data read request, said second storage device transfers, to said switch, data corresponding to the received data read request;
• and
• when receiving the data, said switch transfers the received data to said computer as data transferred from said first storage device.

A switch that is connected to a computer, a first storage device, and a second storage device, said switch comprising:

• a port unit that is connected to an external device;
• a converter for converting commands and data which have been received by said port unit;
• and
• a switch unit for relaying said command and said data according to address information;
• wherein said converter beforehand transfers data stored in said first storage device to said second storage device, and when receiving from said computer an access request for the data stored in said first storage device, said converter converts the access request into an access request to said second storage device;
• said switch unit transmits to said second storage device through said port unit the access request to said second storage device;
• and
• when receiving data corresponding to said access request from said second storage device, said converter converts the data into data transmitted from said first storage device, and then transfers the converted data to said computer.