UPS is an abbreviation for Uninterruptible Power Supply or Uninterruptible Power Source. That is a battery which is used to power a personal computer or a hosting server in order to avoid the loss of data if the main source of energy fails for some reason or becomes risky. A diesel generator pretty much self-explanatory. UPSs and generators are used as a backup in data centers to back up the main power source and to guarantee the continuous operation of all the servers located there. Due to the fact that the UPS works at all times, it provides the required power for the web servers to remain functioning until the generator starts and takes over. Using such a backup is a must for any data center or service provider that wants to keep their hardware and information intact in case of a power surge or outage, due to the fact that it provides them with ample time to react until the issue is resolved and the main power supply is restored.