The UPS and the diesel generator are 2 devices for keeping a server functional if there are issues with the primary source - a disruption or shaky current that cannot keep the hosting server functional, for instance. UPS is an abbreviation for Uninterruptible Power Supply, even though it can often be referred to as Uninterruptible Power Source as well. The UPS is, in essence, an efficient battery that is attached to the machine and to the power network constantly, so in the case of any disturbance, it's already working, which enables the web server to keep on working without losing any info. The diesel generator is an engine that will power up the entire data center. It needs some time to start working and it is the UPS which gives it this time. These 2 power solutions are a necessity for any facility or provider that wants to avoid info loss and hardware damage as a consequence of an unexpected electrical power issue.