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

February 9, 2023

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 center environments that can withstand and offset the risk of service disruptions. This is where data center redundancy can help.

What is data center redundancy?

Redundancy refers to a system design where a component is duplicated so that in the event of a component failure, IT equipment is not impacted. For example, having redundant power in case there's a power outage. The main goal of redundancy is to ensure zero downtime, even in worst case scenarios.

Why is data center 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 is 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 components in ensuring data is safe and secure. Having a well-planned redundancy design implemented into your data center environment is one of those crucial components. System failures can have serious and direct impact on an organization's bottom line, business operations, and customer experience, resulting in devastating revenue loss, missed business opportunities and a tarnished reputation. According to an annual survey conducted by the Information Technology Industry Council (ITIC), 98% of organizations say that a single hour of downtime costs over $100,000. Beyond dollar signs, downtime can severely impact the productivity of your workforce when they're tied up with frantically trying restore systems and data instead of focusing on other core focus areas for your business.

What are the different data center redundancy levels?

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?

N definition

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.

N+1 definition

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.

2N definition

2N refers to a fully redundant, mirrored system with two independent distribution systems. They are not connected in any way and are not 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.

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. We have a team of experts that can help at any time and provide our recommendations as it applies to your specific deployment.