UPSs and diesel generators are two backup systems which are kept by hosting service providers inside their data centers in the event that there are interruptions in the primary power supply or the current is unsound and unable to sustain the appropriate running of the web servers based in the facility. UPS refers to Uninterruptible Power Supply or Uninterruptible Power Source and it is an effective battery which works non-stop. It is connected to both the power network and the servers all of the time, so if the power stops, the UPS is already functioning, which helps prevent the web servers from going down even for a second. The diesel generator is an engine that can supply the needed power to keep the servers operational for a longer period of time. In the case of an outage, the UPS provides the needed time for the diesel generator to start and then to take over until the main power source is restored.