Vertical vs. Horizontal Scaling: The Ultimate Comparison

A growing company or organization will eventually need to expand its operations. When this happens, there are many factors to consider – but no matter what, the goal is to scale.

To remain competitive, companies must continue to redesign their hardware, software and entire infrastructure. This helps you accommodate a growing customer base and meet the new demands of your users.

Both system sizing options – vertical scaling and horizontal scaling – allow companies to improve their performance, productivity and efficiency. But which scalability option is best for your organization?

Here, we'll delve deeper into these system scaling options, sharing the advantages, disadvantages, and a general comparison guide between vertical (scaling up) and horizontal (scaling out) scaling.

The Basics of System Sizing

Before we delve into what it means to scale vertically or horizontally, let's take a look at the holistic concept of scaling an existing machine.

What is system scaling?

System sizing is essentially the process of considering an increase in load and traffic on an existing infrastructure and ensuring simple, hassle-free expansion of resources and performance.

It is critical to efficiently support growing demand, especially with limited hardware resources. This requires the installation of more or better machines. It also involves business software updates, which ensure better UX and agility and lower maintenance costs.

The Two Main Types of Sizing

There are two main types of scaling: vertical and horizontal. Although the vertical scale refers to the concept of “magnification”, the horizontal scale means “magnification”.

As we discuss the differences between these two types of scaling, you will see that the choice between these types will depend entirely on specific use cases and requirements. So let's learn more about vertical and horizontal scaling.

Diving Deep into Vertical Scale (Magnification)

Let's look at vertical scaling, its main features, advantages and disadvantages in more detail.

Definition and main characteristics

Vertical scaling is essentially the process of improving existing infrastructure to meet increased demand. Expansion does not require companies to change their software applications. This is because the same application now runs on a much more powerful infrastructure.

Instead, vertical scaling involves increasing memory, storage, and server capacity or replacing an outdated server with a new one. Now, let's take a look at the benefits and limitations of vertical scaling.

Advantages of vertical scaling

Here are the main benefits of scaling vertically:

• Simplicity of configuration

With this type of scheduling, a single node is responsible for taking care of the entire process. As a node manages all layers of services, vertical scaling eliminates the need for synchronization and communication with other servers to function. Additionally, the lack of complexity makes it easier to maintain a vertically scaled infrastructure.

• Direct performance improvement

Expansion comes with direct performance improvement because multi-core leads to scalability. Since all data is stored on a single machine, vertical scaling decreases the chances of data inconsistency. You can multiply processing power by installing cutting-edge processors and servers.

• No need for code changes in some cases

Vertical scaling improves overall infrastructure performance without the need to add more processing units or hardware. This is also because there are minimal changes to the web service code. In other words, we are increasing the processor's capacity to make the same code run more efficiently.

Disadvantages and Limitations

There are still some limitations to vertical scaling, of course. They include:

• Hardware Limits

You can make processor upgrades to increase the computing capacity of your infrastructure. However, you can only increase the processing power to the limit of the operating system and updates can be indefinite. You can only install the latest updates given the machine's RAM, storage, and processing power limit.

• Downtime during updates

With vertical scaling, you run the entire process using a single machine. This makes it difficult to update the system frequently, as the update process entails considerable downtime. Downtime can be reduced by installing a backup server that can temporarily handle operations and requests.

• Increased risk of a single point of failure

Because scaling up performs all operations on a single server, you run the risk of a single point of failure. In other words, there is a risk of significant data loss if the hardware or software fails.

Diving deep into the horizontal scale (horizontal scale)

Now, let's discuss horizontal scaling, its main features, advantages and disadvantages in detail.

Definition and main characteristics

Horizontal scaling refers to the idea of ​​“expansion”. It is essentially the process of multiplying the available infrastructure by increasing the number of machines, servers or nodes in the resource pool in order to equally distribute the computational workload. Scaling involves strategies such as load balancing, clustering, and file system distribution.

With this type of scaling, you have the opportunity to improve I/O concurrency while reducing the load on existing nodes.

Advantages of Horizontal Scaling

This type of sizing has many advantages. Key benefits include:

• Improved fault tolerance

Operations run on a horizontal versus vertical scale tend to be more resilient and reliable. This is because adding more computing units to the infrastructure means that the system is not dependent on a single node. Expansion comes with improved fault tolerance because operation is distributed equally across multiple nodes.

• Scalability beyond hardware limits

Remember: Vertical scaling does not allow for scalability beyond the operating system's capabilities. With horizontal scaling, you can overcome this limitation by adding more compute units to your infrastructure. In other words, scaling becomes easier as we add more hardware to the current resource pool. You can upgrade individual compute units while achieving maximum vertical scaling.

• Load distribution

It is important that this type of scaling facilitates load balancing and distribution to ensure effective traffic management for different machines. The idea is to place an equal load on each node and achieve equal load distribution. Load distribution increases system upgradability as scaling does not result in downtime as we are no longer limited to the capacity of a single drive.

Disadvantages and Limitations

As with vertical scaling, there are some disadvantages to this type of scaling:

• Complexity in configuration and maintenance

It is common to face complexity in maintenance and configuration with horizontal scalability. This is because you are adding more operating units or nodes to the infrastructure. In addition to hardware upgrades, you may need to add additional software features for load balancing and virtualization. At the same time, you would need to ensure effective synchronization of nodes to facilitate continuous communication.

• Possible data consistency issues

Because each node in the horizontally scaled system serves different requests, data sharing and communication often fall out of sync. This results in data inconsistency, which must be resolved immediately to ensure efficient processing and operation.

• Requirement for load balancing

Ideally, the added hardware will have equal computing power. Otherwise, scaling will have to facilitate a load balancer to distribute traffic among all nodes. With load balancing, you must ensure that the system does not go down if one of the nodes does not work.

Horizontal and Vertical Scaling: A Side-by-Side Comparison

Here are the three main factors that will help you decide between horizontal and vertical scaling:

Cost implications

Horizontal scaling is more expensive than vertical scaling because it involves higher upfront hardware costs and requires re-architecting a software system. Companies with limited budgets should opt for vertical scaling because an increasing number of powerful multi-core machines are now packaged in a single box. In other words, you can get performance and scalability without breaking the bank.

Performance and Reliability

Performance will depend entirely on your software infrastructure and specific requirements. If you have a simple application to run, horizontal scaling would not be an ideal choice as running the application on multiple machines may even degrade its quality.

Simply upgrading hardware (vertical scaling) could help meet growing demand. However, horizontal scaling is more reliable than vertical scaling because it involves multiple machines that can share the computational workload.

Scalability potential

Scalability or long-term upgradability is an important factor that differentiates horizontal and vertical scaling. Horizontal scaling allows for a continuous upgrade process that, unlike vertical scaling, does not require the entire system to be decommissioned.

Real use cases and industry examples

Let's discuss some use cases for both scaling options to help you determine which scaling model is right for your business.

Successful vertical scaling implementations

Vertical scaling is a good option for newer businesses because they are still in the early stages of building traffic and a user base. This is also useful for companies planning fewer updates.

Expansion is appropriate if increasing machine capabilities results in a cost-effective performance upgrade. Companies like MySQL, Amazon RDS, SAP HANA VMware, Hyper-V, SAP ERP, Microsoft Dynamics and others use vertical scaling.

Successful scale-out implementations

Horizontal scaling is the best choice for companies that want to upgrade quickly and frequently without causing significant downtime. Expansion helps reduce single points of failure.

Most importantly, horizontal scaling is advisable for companies that utilize a microservices architecture and for those that have sufficient resources to acquire and maintain additional hardware and software.

Companies like Amazon, Airbnb, Spotify, Netflix, Twitter, Cassandra, MongoDB, Google, Cloud Spanner and many others use horizontal scaling.

Conclusion

The two scalability options differ in terms of performance, cost, flexibility, reliability, upgradability, and other critical factors. It is important for companies to specify their compute workload requirements to make a solid decision when sizing.

Common questions

What does it mean to size a system?

Scaling a system means adding or removing infrastructure resources to ensure efficient business operations and meet an increase or decrease in demand.

When should a company consider vertical scaling?

Vertical scaling is preferable when increasing machine capacity results in improved performance. Companies just starting out should use vertical scaling, especially if they want to offer few and far between updates.

How does horizontal scaling improve fault tolerance?

Because horizontal scaling ensures that more than one server shares the computational workload, a failure on any one server will not result in downtime because others are ready for backup.

Are there cost benefits to one scaling method over the other?

Scaling up is more cost-effective than scaling out because scaling involves higher initial hardware expenses, licensing fees, and utility costs, and requires re-architecting the software system.

Can a system use vertical and horizontal scaling simultaneously?

Companies should seek to move between horizontal and vertical scale. This allows them to benefit from both paradigms. For example, teams can modify their existing set of machines using memory upgrades, installing multiple RAMs on a system while planning to increase the capacity of each of the installed RAMs.