There is disclosed a high speed switching method for a disk image delivery system fail-over. A management server sends a disk image of an active server in advance to a standby server. When receiving a report that the active server has failed, the management server judges whether or not it is possible for the standby server to perform the service of the failed active server based on service provision management server information held by the management server and if possible, instructs the standby server to perform the service of the active server. Even if the disk image delivered in advance is different from the disk image of the failed active server, switching of the service to the standby server can be performed more quickly through resetting the setting values of unique information and installing the additional pieces of software on the standby server by the management server than redelivering an appropriate disk image.