UPSs and diesel generators are 2 backup systems that are kept by hosting providers within their data centers in the event there are interruptions in the main power supply or the current is shaky and unable to support the proper operation of the machines located in the facility. UPS refers to Uninterruptible Power Supply or Uninterruptible Power Source and it is an efficient battery that works non-stop. It is connected to both the power network and the servers all of the time, so when the power stops, the UPS is already up and running, which helps prevent the machines from going down even for a second. The diesel generator is literally an engine that can deliver the required electrical power to keep the web servers functioning for a longer period of time. In the case of 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.