A system includes a bus, multiple BMCs, and a control unit. Each BMC generates heartbeat signals and acquire operation data associated with a to-be-monitored unit once being initiated, and operates in one of a master mode and a slave mode according to a corresponding decision signal. One of the BMCs which operates in the master mode is configured to receive via the bus the operation data from the rest of the BMCs which operate(s) in the slave mode for monitoring the to-be-monitored unit. The control unit is configured to, according to the heartbeat signals, generate the corresponding decision signals for controlling a first normally operating one of the BMCs to operate in the master mode and the rest of the BMCs to operate in the slave mode.