A method, data processing system and computer program product provide scalable data synchronization for a virtual input/output server (VIOS) cluster and one or more registered callers. A first VIOS is commits as a primary node of the VIOS cluster and performs the functions of: registering one or more callers to receive notification from the first VIOS of specific events occurring within the cluster; receiving notification of an occurrence of one of the specific events; and in response to receiving notification of the specific events, a deamon of the first VIOS retrieving a message payload file from a message payload file directory within the shared VIOS DB and passing the message payload file to the API, which forwards/posts the relevant event notification information from the message payload file to the TCP socket of each registered caller.