UPS is an abbreviation for Uninterruptible Power Supply or Uninterruptible Power Source. It is a battery which is used to power a personal computer or a web server in order to avoid the loss of data in case the main source of energy fails for reasons unknown or becomes unsafe. A diesel generator practically self-explanatory. UPSs and generators are widely-used as a backup in data centers to back up the main power source and to guarantee the uninterrupted running of all of the servers located there. Because the UPS works at all times, it provides the desired power for the web servers to remain operational until the generator starts and takes over. Using this type of a backup is vital for any data center or provider that wants to keep their hardware and information intact in case of a power surge or outage, because it offers them lots of time to react until the issue is resolved and the main power supply is restored.