SERVER, SERVER SYSTEM, AND SERVER REDUNDANCY SWITCH METHOD

PROBLEM TO BE SOLVED: To provide a control server capable of recovering a server system including one or more active physical servers and standby physical servers at an early stage when a failure occurs in the server system.SOLUTION: A control server 300 includes: means for monitoring operation states of plural active servers running therein OSs 200, 210, and 220 for operating applications that generate, delete, and refer to data; means for synchronizing data of the OSs 200, 210, and 220 in the active physical servers with that of a standby server running on a host OS 240 guest OSs 242, 244, and 246 corresponding to the OSs in the active servers; and means for, when the monitoring means detects a failure in the operation state of one of the active physical servers, starting the application having operated in the one of the active physical servers on a corresponding one of the guest OSs 242, 244, and 246, and switching a system from the active server where the failure has been detected to the corresponding one of the guest OSs 242, 244, and 246 in the standby server.