According to the How to use the cvm_shutdown script web search result3, the cvm_shutdown script signals HA when shutting down the CVM (Controller VM) to forward the storage traffic to another healthy CVM.
Instead of using sudo shutdown or sudo reboot commands, this script should be used to minimize I/O hits in user VMs running on the present hypervisor host. The cvm_shutdown -P now command will initiate the shutdown process on the CVM immediately. Therefore, if the administrator needs to perform an orderly shutdown of the CVM, they should execute this command from the CVM.