Release Notes for High Availability
Synology High Availability uses two Synology servers to construct a high-availability cluster (HA cluster), with one server being the active server and the other one being the passive server for failover. The active server takes care of all the services and replicates data to the passive server. If the active server fails, the passive server will be promoted to be the new active server and starts taking over the services handled by the original active server.