The UPS and the diesel generator are two means for keeping a web server working if there are troubles with the primary power source - an interruption or unstable current that cannot keep the server functional, for instance. UPS is an abbreviation for Uninterruptible Power Supply, though it can often be referred to as Uninterruptible Power Source also. The UPS is, basically, a powerful battery that is attached to the server and to the electric power network at all times, so in case there is any blackout, it is already operating, which allows the server to carry on operating without losing any info. The diesel generator is an engine which can power up a whole data center. It does take some time to start working and it is the UPS which gives it that time. Those 2 power solutions are a necessity for any facility or hosting company that wants to stop information loss and hardware damage as a result of an unexpected electric power problem.