Which of the following understanding of the working principle of high availability cluster is correct? (Multiple choice)
A . computing system high availability to measure by the system reliability and maintainability
B . High availability cluster has two working modes: Active-Active working mode and Active-Standby working mode
C . In the Active-Standby high-availability cluster, the standby server detects the operating status of the master server through a heartbeat line, but it cannot detect the "heartbeat" of the master server, and then automatically takes over the resources of the master server.
D . High-availability cluster refers to the use of the fault tolerance of the cluster system to provide 7*24 hours of uninterrupted service to the outside, designed to provide highly reliable services
Answer: ABCD