The UPS and the diesel generator are two means for keeping a web server functioning if there are difficulties with the main power supply - a disruption or unreliable current which cannot keep the hosting server working properly, for example. UPS is an abbreviation for Uninterruptible Power Supply, though it is sometimes referred to as Uninterruptible Power Source as well. The UPS is, basically, a highly effective battery which is attached to the web server and to the power network all the time, so in case of any blackout, it is already functioning, which enables the hosting server to carry on operating without losing any information. The diesel generator is an engine which will power up the whole data center. It does take some time to begin working and it's the UPS that gives it that time. Those two power solutions are absolutely essential for any facility or hosting company that wants to avoid information loss and hardware damage as a result of an unexpected electric power problem.