Redundancy is simply a backup. Network managers deploy redundant servers to ensure continuous data availability. E3 Series 3-Phase UPS Systems deliver redundancy both internally and externally to provide continuous power availability. Redundancy is often referred to in terms of "N", "N+1", "N+2", and many more. In simple terms, "N" is what it needs to get the job done. "N+1" is what it needs to get the job done, plus a little more. Cars provide a common example of N+1 redundancy. Four tires (N) are required to support a standard car; however, one spare tire (+1) is usually included if one of the tires fails or is removed for maintenance. "1+1" redundancy (also known as "N+N") goes one step further. Instead of providing "just a little more" to get the job done, it provides an entire identical system as a backup. Going back to the car as a common example of 1+1 redundancy. One brake system (1) is required to stop a car; however, one emergency brake system (+1) is included if the main system fails.