Comparing 2N vs N+1 Redundancy: Which Is Better for Your Data Center?

In a world that is only always “on”, high costs are associated with downtime. According to a Poneman Institute report, the average cost of a data center outage is USD 9,000 per minute. A rapid response to the outage is key to mitigating downtime and escalating costs. Minutes count.

There are various levels of redundancy, with the two most common types being N+1 and 2N. In this article, we compare these two redundancy strategies to help you determine which one is better suited for your data center.

Understanding the N Model

The ‘N’ equals the amount of capacity required to power, backup or cool a facility at full IT load. N can represent the units that are to be duplicated such as a generator, UPS, or cooling unit. If a data center requires 4 UPS units to operate at full capacity, N would equal 4.

N is the same a zero redundancy. None of the components are duplicated and in the event of an outage, or there is a hardware failure, or a scheduled maintenance, mission critical applications would suffer, and business operations would be down until the issue is resolved. This could result in a massive loss of business and reputation for many organizations.

Understanding N+1 Redundancy

In the context of data centers, N+1 redundancy refers to additional components (the ‘+1’) to cover the number of components necessary for the system to function (the ‘N’). Using the above example, if N equals four UPS units, N+1 provides 4 making a total of 8.

The additional (or spare) component supports a failure and maintains full data center operations. If one of the components fails, the spare takes over instantly to maintain operations. This system provides a reliable backup that ensures continuity of service and provides time to replace or repair the failed component.

Understanding 2N Redundancy

The 2N redundancy strategy takes reliability to the next level by duplicating every component in a system. While N+1 redundancy model delivers the needed protection for most organizations, there are some sectors that require a greater safety net, such as healthcare and financial sectors. The 2N redundancy model offers a more robust infrastructure for these organization. The 2N model represents a completely independent, mirrored system of UPS, cooling systems, generators capable of taking over operational needs if the primary system were to suffer outage. Two independent distribution systems, each capable of carrying the full operational load, provide additional safeguard.

As a result, 2N redundancy provides a higher level of fault tolerance and assures continuity of operations, even if an entire system fails.

N+1 vs 2N Redundancy: A Comparison

Medium to large size businesses should consider N1 redundancy whereas N2 Redundancy is a necessary for larger businesses that rely on multiple data centers to execute their services. However, other factors worth considering include:

• Cost and Resource Utilization: With each increase in redundancy, the price goes up. While N+1 redundancy is less costly it does not require an exact replica of every component. N1 redundancy uses fewer resources, which can lead to savings in energy and space.

  The 2N redundancy requires double the resources, as well as additional costs in staffing, maintenance and upgrades. This significantly increases the costs of N2 redundancy.

• Reliability and Fault Tolerance: N+1 redundancy provides a reliable backup for most of the business. However, the 2N offers a higher level of reliability because the entire data center can still function, even if a system fails completely. For mission-critical applications, the 2N redundancy is usually the preferred choice.
• Maintenance and Upgrades: With 2N redundancy, one system can continue to carry the operational load while maintenance or upgrades are performed on the other. In contrast, with N+1 redundancy, certain operations may need to be paused or rescheduled during maintenance or upgrades.

Which Is Better for Your Data Center?

The top priority of every data center should maximum uptime, be they small or hyperscale. To keep your data center constantly running, a plan for redundancy systems is a must. As such there is no right or wrong redundancy model. The choice between N+1 and 2N redundancy comes down to your specific needs, including your budget, risk tolerance, and the critical nature of your applications.

Both N+1 and 2N redundancy offer effective strategies to ensure uptime in data centers, but they come with different levels of investment, resource requirements, and reliability. By understanding the differences between the two, you can begin considering which redundancy strategy is best suited for your data center’s needs.