Whether you are running a personal desktop computer, or a major data center facility, electricity is one thing that all computers need to have. Even a very brief power outage will disrupt any system, and in some cases, can even damage the equipment. This is why many critical systems have devices known as redundant power supplies built right in. Redundant power supplies are most commonly found in servers, blade chassis, large network equipment, and other essential items.
Understanding this type of power supply will help ensure your computer equipment is up and running at all times.
What is a Redundant Power Supply?
A redundant power supply is when a single piece of computer equipment operates using two or more physical power supplies. Each of the power supplies will have the capacity to run the device on its own, which will allow it to operate even if one goes down. 
For normal operation, each of the power supplies will provide half (assuming there are two) of the power that is needed. If one is powered off for some reason, the other one will immediately compensate to provide full power to the device so there is no downtime at all.
The one downside to a redundant power supply setup is that it takes up more room within the device itself. This is why they are only used in situations where uptime is extremely important. By eliminating this single point of failure, the systems running on the device will be available for users a much greater percentage of the time.
Hot Swapping
In the event that one of the power supplies stops working, you will typically be able to replace it without taking the device offline. Equipment that operates using multiple power supplies will allow you to simply unplug the defective power supply, physically remove it from the device, and then slide a new one in and plug it back in. The second power supply will continue to keep the device operating the entire time so users of that device will never have to know there was a problem.
Separate Power Circuits
For situations where you want to be certain that a device will have power at all times, it will be necessary that each of the redundant power supplies operates on a separate electrical circuit. This will allow the device to continue to run even during a circuit trip or other issues.
Running two separate power circuits to each power supply also allows you to perform maintenance and other work on the electrical equipment without taking the device offline. This setup is especially ideal for when uptime is critical.
Redundant Power Supplies vs Uninterrupted Power Supplies
There are two similar terms related to power supply that aren’t actually the same thing, and this often causes confusion. The first, of course, is the redundant power supply. The other is an uninterrupted power supply, or UPS. Unlike a redundant power supply, a UPS is a separate unit that is not a part of any other device.
Instead, a UPS provides continuous electricity, even when commercial power is out. For a personal computer, a UPS can be a small device that serves as a battery backup. The UPS offers continuous electricity until it runs out of juice, or the commercial power comes back up. Virtually all data centers have a major UPS system that often has a battery-based backup system and a diesel generator. This allows the facility to operate indefinitely, even without utility power.
Using Redundant Power Supplies
If you have any equipment that uses a redundant power supply, it will likely be housed in a data center. The average desktop computer, and even most servers, don’t require this type of hardware to be used. Fortunately, taking care of a redundant power supply is no more difficult than a single supply. Simply make sure they are clean and provided with a good source of power, and they will ensure your computer equipment is up and ready to go at all times!