UPSs and diesel generators are 2 backup systems which are kept by web hosting companies within their data centers in the event that there are interruptions in the primary power source or the current is unsound and unable to support the proper operation of the machines located inside the facility. UPS stands for Uninterruptible Power Supply or Uninterruptible Power Source and it is an efficient battery which works non-stop. It is connected to both the electrical power network and the servers consistently, so if the power stops, the UPS is already up and running, which prevents the web servers from going down even for a second. The diesel generator is definitely an engine that can give you the necessary electrical power to keep the servers up and running for a longer period of time. In case there is an outage, the UPS gives the required time for the diesel generator to start and then to take over until the primary power supply is restored.