2N vs. N+1: Data Centre Redundancy Explained

As technology continues to advance into every aspect of how businesses operate day-to-day, so does the potential risk and impact of any downtime. To ensure uptime and continuity, businesses need to consider data centre environments that can withstand and offset the risk of service disruptions. This is where data centre redundancy can help.

What is data centre redundancy?

Redundancy in data centres means having backup systems and components that can take over immediately if the primary system fails. This can help reduce the impact of outages, ensuring that services remain available, and downtime is minimised. There are different strategies for implementing redundancy, each with its own advantages and disadvantages.

Why is data centre redundancy important?

The maximum tolerable period of disruption (MTPD) is continuing to decrease for most companies because there is less tolerance for their operations experiencing any sort of downtime. There's growing pressure and necessity for companies to be able to maintain uptime and recover more quickly from a disruption, no matter how it was caused.

There are many factors in ensuring data is safe and secure. Having a well-planned data centre redundancy design implemented into your data centre environment is one of those crucial components. System failures can have a serious and direct impact on an organisation's bottom line, business operations, and customer experience. This can result in devastating revenue loss, missed business opportunities, and a tarnished reputation.

In 2014, Gartner estimated that organisations lost an average of $300,000 per hour due to downtime. Yet, recent data starkly contrasts this six-figure sum, revealing that 44% of organisations now experience hourly downtime costs exceeding $1 million, not including subsequent penalties or legal fees.

What are the different data centre redundancy levels?

Among the most common redundancy strategies are N+1 and 2N. The decision to implement N+1 or 2N redundancy is based on a variety of factors, including the criticality of the IT services, cost considerations, and the desired level of availability.

Before building a redundant architecture, it's important to understand the different capabilities and risks of each data center redundancy level. Let’s define them – this includes N, N+1 and 2N.

So, what is the difference between 2N vs. N+1?

What is N?

The term “N” simply represents the unit that you wish to duplicate – whether it’s a generator, UPS, or cooling unit.

N equals the amount of capacity required to power, backup or cool a facility at full IT load. A design of N means the facility was designed only to account for the facility at full load and zero redundancy has been added. If the data center facility is at full load and there is a component failure or required maintenance, mission critical applications would suffer.

What is N+1 redundancy?

If N equals the amount of capacity needed to run the facility, N+1 indicates an additional component added to support a single failure or required maintenance on a component. Design standards typically call for 1 extra unit for every 4 needed. So if you have, say, 8 UPS units, then you should at least have 10 total UPS units.

What are the advantages of N+1 redundancy?

Cost-effectiveness

N+1 redundancy is a more cost-effective alternative to 2N redundancy. By incorporating one redundant component for every N active components, we can achieve a robust level of fault tolerance without the burden of excessive costs.

Simplicity

N+1 redundancy is easier to implement and manage than 2N redundancy. With fewer redundant components, there are fewer points of failure and less complexity in the system, making it easier for IT teams to maintain and troubleshoot.

Scalability

N+1 redundancy is more scalable than 2N redundancy. As businesses grow and their IT requirements expand, it's easier to add redundant components to a N+1 system to maintain the desired level of redundancy.

What is 2n redundancy?

2N refers to a fully redundant, mirrored system with two independent distribution systems. They aren't connected in any way and aren't dependent on each other. This means that even if one power source has an interruption or loss of power, the other should still supply power and accommodate full load, thereby eliminating any potential downtime from the loss of one side or leg of the system.

What are the advantages of 2N redundancy?

Highest Availability

2N redundancy is the most robust redundancy strategy. By mirroring all components, 2N redundancy guarantees uninterrupted operation even in the face of multiple component failures.

Maximum Fault Tolerance

2N redundancy ensures the highest level of fault tolerance. By duplicating all components, we guarantee that a redundant part is always ready to take over in case of a failure, maintaining the continuity of IT services.

How to choose the right redundancy configuration

There’s no right or wrong redundancy configuration since it depends on many factors like your IT environment, business goals, and budget. We always recommend having this discussion with your account rep, sales engineer and solution architect to figure out the best option for you.

Digital Realty's data centres are designed to meet the highest standards of reliability and performance, offering both 2N and N+1 redundancy configurations to suit diverse business needs. With 2N redundancy, our colocation facilities provide the highest level of fault tolerance and uninterrupted operation, ensuring that even in the face of multiple component failures, your critical IT services remain online.

For businesses seeking a cost-effective yet robust solution, our N+1 redundancy offers a scalable and simpler alternative, incorporating one redundant component for every N active components. This flexibility allows us to support a wide range of industries, from financial services to healthcare, ensuring that your data remains secure and your operations uninterrupted.

Whether you need the maximum availability of 2N or the cost-effectiveness of N+1, Digital Realty's data centres are equipped to provide the optimal solution for your specific requirements. Contact our team of experts who can help at any time and provide recommendations as it applies to your specific deployment.