UPS is used to protect server from power failure. As server running, it is keeping read and write data to hard disk whether users is accessing server or not. when power failure occur, server may not have enough time to finish data writing and cause data lost. In worst case, it may corrupt OS section of server and cause server cannot start up again. Beside data loss, power failure may also cause some hardware damage.

UPS is important in power failure, since it will keep server powered during power failure. then UPS will send signal to ask server to shutdown. Server will have enough time to save its data to disk in order to protect server from unexpected shutdown.