UPSs and diesel generators are two backup systems that are kept by web hosting companies within their data centers in the event that there are interruptions in the main power supply or the current is unstable and unable to maintain the appropriate running of the servers situated 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 web servers consistently, so if the power stops, the UPS is already operational, which prevents the machines from going down even for a second. The diesel generator is literally an engine which can deliver the required electrical power to keep the web servers working for a longer period of time. In the case of an outage, the UPS provides the required time for the diesel generator to start and then to take over until the primary source is restored.