A redundancy method implemented in an information processing device that performs communication using a first communication method and using a second communication method that is faster than the first communication method, the redundancy method comprising: performing equalization operation using the first communication method with respect to a first information processing device in a redundancy system in which redundancy is achieved between the first information processing device and a second information processing device using the first communication method; building that includes performing, after completion of the equalization operation, equalization operation using the second communication method with respect to a third information processing device, and building a redundancy system in which the information processing device and the third information processing device are used; characterized in that the method further includes performing negotiation using the first communication method, and determining whether or not the third information processing device has adapted the second communication method, wherein when it is determined that the third information processing device has adapted the second communication method, equalization operation is performed using the second communication method, and when it is determined that the third information processing device has not adapted the second communication method, equalization operation is performed using the first communication method. performing equalization operation using the first communication method with respect to a first information processing device in a redundancy system in which redundancy is achieved between the first information processing device and a second information processing device using the first communication method; building that includes performing, after completion of the equalization operation, equalization operation using the second communication method with respect to a third information processing device, and building a redundancy system in which the information processing device and the third information processing device are used; characterized in that the method further includes performing negotiation using the first communication method, and determining whether or not the third information processing device has adapted the second communication method, wherein performing, after completion of the equalization operation, equalization operation using the second communication method with respect to a third information processing device, and building a redundancy system in which the information processing device and the third information processing device are used; characterized in that the method further includes performing negotiation using the first communication method, and determining whether or not the third information processing device has adapted the second communication method, wherein when it is determined that the third information processing device has adapted the second communication method, equalization operation is performed using the second communication method, and when it is determined that the third information processing device has not adapted the second communication method, equalization operation is performed using the first communication method.