What is the Difference Between Horizontal and Vertical Scaling

The main difference between horizontal and vertical scaling is that the horizontal scaling refers to adding multiple computing devices or nodes to the system to improve performance while the vertical scaling refers to adding more resources to a single computing device to improve performance.

Scalability refers to handling the growing amount of work in a capable manner. In other words, it is the capability of a system, network or a process to handle the growing work. Scalability can be applicable to hardware as well as software. In order for a system to handle more work, it should either receive more power or there should be more systems. There are two types of scaling called horizontal and vertical scaling. Horizontal scaling is adding more devices to the system while vertical scaling is adding more resources to a single device. Both these methods increase the system performance, but horizontal scaling is more cost effective and easier to implement than vertical scaling.

Key Areas Covered

1. What is Horizontal Scaling
     – Definition, Functionality
2. What is Vertical Scaling
     – Definition, Functionality
3. What is the Difference Between Horizontal and Vertical Scaling
     – Comparison of Key Differences

Key Terms

Horizontal Scaling, Scalability, Scaling Out, Scaling Up, Vertical Scaling

What is Horizontal Scaling

Horizontal scaling refers to adding more and more nodes or computing devices to the system. It is also called scaling out. More nodes will make the system more powerful. There is a linear correlation between the number of computers and the performance. For example, if a single system can process some amount of data, a system with five devices can process data five times faster. Moreover, the computing devices used in horizontal scaling are usual commodity computers. These commodity computers are cost effective. Therefore, it is less expensive to implement horizontal scaling in order to create a high-performance system.

What is Vertical Scaling

Vertical scaling refers to adding more resources to the existing computing device or the node. It is also called scaling up. If it is required to process more amounts of data at a time, it is possible to use more CPUs and more memory. If it is required to add more storage, it is possible to add more disks. One application of vertical scaling is adding more resources to a single computing device and using that device to create multiple virtual computers.

Figure 1: Horizontal and Vertical Scaling

Vertical scaling helps to improve the system performance. On the other hand, its major drawback is that it is only possible to make the system powerful until a certain point. For example, vertical scaling is not suitable for handling big data because a single powerful system is not enough to handle a huge amount of data.

Difference Between Horizontal and Vertical Scaling

Definition

Horizontal scalability is the ability to increase capacity by connecting multiple hardware or software entities so that they all work as a single logical unit. Vertical scalability is the ability to increase the capacity of existing hardware or software by adding resources. This explains the basic difference between horizontal and vertical scaling.

Synonyms

Scaling out is another name for horizontal scaling while scaling up is another name for vertical scaling.

Cost

Horizontal scaling is cost-effective than vertical scaling because it is easier to add multiple computing devices rather than making a single device powerful to handle processing. This is a major difference between horizontal and vertical scaling.

Applications

Furthermore, while horizontal scaling is used in distributed systems, vertical scaling is used in virtualization.

Conclusion

The difference between horizontal and vertical scaling is that horizontal scaling is adding multiple computing devices or nodes to the system to improve performance while vertical scaling is adding more resources to a single computing device to improve performance. Today, commodity computers are cheaper and powerful and applying horizontal scaling is more effective.

Reference:

1. Overview of Scalability, Horizontal Scaling, and Vertical Scaling, HandsonERP, 1 May 2013, Available here.
2. “What Is Vertical Scalability (Scaling up)? – Definition from WhatIs.com.” SearchCIO, Available here.