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Alliance SI’s guide to N, N+1, 2N and 2N+1 redundancy


By Alliance SI Insights
Data center with auxiliary communications

One of the most important aspects of data centre infrastructure is evaluating the capabilities of your facility. This is especially true for data centre redundancy.

Redundancy is a major point of emphasis for data centres because a component failure can have serious consequences. When systems fail, data and services are no longer available to the businesses and customers that rely upon them.

Many data centres use specific terminology to describe a facility’s redundant systems and its overall capabilities, and redundancy terminology involves a few different levels.

To quickly understand redundancy, data centres describe redundancy levels as N, N+1, 2N and 2N+1. We break down what each redundancy level means and how it applies to your data centre network infrastructure and design.

N redundancy


The N redundancy level is the amount required for operation. The symbol ‘N’ represents the amount of infrastructure needed to operate your facility at a full IT load. N redundancy is typically used to describe cooling units or uninterrupted power supplies (UPS), but it can also apply to many other aspects of data centre infrastructure.

It’s important to remember that N redundancy is the baseline capacity. A data centre with N capacity has everything it needs to operate as designed, but it has no redundancies in place to accommodate equipment failure or maintenance. If the system fails, downtime is the end result.

Cooling towers in data center

N+1 redundancy


Unlike the base N redundancy level, an N+1 redundancy means that your facility has the capacity to run a full IT load with an additional component to account for failure or maintenance.

As an example, when you get a flat tyre, N+1 redundancy can swap out the flat with a spare, working tyre. The N+1 redundancy must be able to sustain the failure without degradation in capacity or performance.

N+1 redundancy standards typically require an extra unit for every four needed, so if 12 cooling units are required, an N+1 facility would have 15 units.

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2N redundancy


The 2N redundancy means that you have twice the amount required for optimal operation. A 2N system is fully redundant with a completely independent, mirrored system that can take over operational needs should the first system go offline for any reason.

2N redundancy is typically considered fault-tolerant because it can provide uninterrupted service in the event of a significant failure to one system. 2N systems are also easy to maintain because one system can be shut down for repairs or maintenance while the mirrored system continues to provide for the facility’s needs.

2N+1 redundancy


2N+1 is the highest form of data centre redundancy. 2N+1 systems provide a completely paralleled backup system along with additional components to account for failure and maintenance in each system.

2N+1 offers tremendous versatility because it has full, fault-tolerant redundancy as well as accommodating component failure without completely shifting over to a backup system.

Uninterruptible power supply

Which redundancy level do you need?


Choosing the appropriate level of redundancy can be tricky. While it might sound like defaulting to the highest level of redundancy is the best choice, not every industry or business requires the same uptime and availability standards.

Some businesses could end up paying more for redundancy they don’t really need.

For most businesses, N+1 redundancy is a good baseline that balances high reliability with affordable costs.

Data centre redundancy is vital for businesses to evaluate. Understanding how data centres assess redundancy is a good starting point for evaluating the capabilities of a data centre facility.

With harmful risks such as system downtime, it’s important for businesses to partner with network infrastructure experts who can provide the best data centre redundant systems and support.

Data Centre Infrastructure Experts

Partner with the data centre infrastructure experts


Our experience in data centre infrastructure spans more than 40 years. At Alliance SI, we have the knowledge, management skills and professional technicians to deliver superior results for every project. The Alliance SI team works efficiently within facility guidelines and complex data centre protocols.

We also step inside your business to fully understand your requirements. We take a big picture view of not only your current needs but how we can provide a solution that will support you into the future.

With our knowledge of your complete data centre infrastructure, we are in the best position to service your ongoing redundancy, cabling and maintenance needs.

Contact us to discuss your data centre infrastructure requirements with one of our experienced account managers.

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