UPSs and diesel generators are 2 backup systems which are kept by website hosting companies within their data centers in the event that there are interruptions in the main power supply or the current is unsound and unable to support the proper running of the machines situated inside the facility. UPS stands for Uninterruptible Power Supply or Uninterruptible Power Source and it's an effective battery that works non-stop. It is connected to both the electric power network and the servers all of the time, so anytime the power stops, the UPS is already working, which helps prevent the machines from going down even for a second. The diesel generator is an engine which can provide you with the necessary electric power to keep the machines operational for a longer period of time. In the event of an outage, the UPS provides the required time for the diesel generator to start and then to take over until the main source is restored.