UPS is an abbreviation for Uninterruptible Power Supply or Uninterruptible Power Source. It is a battery used to power a computer or a server to prevent the loss of info when the main power source fails for whatever reason or becomes unsafe. A diesel generator is more or less self-explanatory. UPSs and generators are widely-used as a backup in data centers to back up the power and to ensure the consistent functioning of all the machines located there. Because the UPS works at all times, it offers the required power for the web servers to remain working until the generator starts and takes over. Using this type of a backup is critical for any data center or provider that wants to keep their hardware and information intact in the case of a power surge or outage, due to the fact that it offers them lots of time to react until the issue is resolved and the main power supply is restored.