Patent ID: 7472143

Claim:
A computer system comprising a first network, a first computer connected to the first network, a second network connected to the first network, and a second computer and a third computer connected to the second network, the first computer comprising: a communication interface for connecting the first computer to the first network; a disk storage device for storing data; a disk interface for communicating data with the disk storage device; a CPU for controlling the first computer; and a memory for storing data and program code for operating the CPU, wherein the program code includes: a module for recording situations of access to a file stored in the disk storage device from the third computer, the module being executed by the CPU at predetermined intervals, and wherein the program code is executed depending on the access situation, the program code further including: a module for searching the second network connected to the third computer; a module for searching a candidate for migration for the second network; a module for designating the file as the candidate for migration to the second computer; a module for transmitting a migrator acceptor search packet to the second computer for inquiring whether or not the second computer can accept the file in accordance with a requested storage capacity; a module for receiving a reply packet from the second computer as a response to the migrator acceptor search packet; a module for transmitting an advertisement packet to the third computer either after or before the file is transferred to the second computer, the advertisement packet indicating that the file is transferred to the second computer; a module for transferring the file to the second computer; a module for storing information indicative of whether the file has been transferred to the second computer or the file exists in the first computer; a module for storing a path name for the second computer when the file has been transferred to the second computer; a module for allowing the third computer to access the file via the first computer based on the information and the path name when the first computer receives an access request from the third computer for the file after the file has been transferred to the second computer; a module for receiving a return request packet from the second computer and issuing a read request in response, for returning the file to the first computer; and a module for receiving and storing the file in the first computer, when the file is returned from the second computer.