A growing business or organization will eventually need to expand its operations. When it does, there are many factors to consider—but no matter what, the goal is to scale.
To stay competitive, businesses must continue to overhaul their hardware, software, and entire infrastructure. This helps you accommodate a growing customer base and meet the changing demands of your users.
Both system scaling options—scaling vertically and scaling horizontally—allow businesses to enhance their performance, productivity, and efficiency. But which scalability option is best for your organization?
Here, we will deep dive into these system scaling options, sharing the advantages, disadvantages, and an overall comparison guide between scaling vertically (scaling up) and horizontally (scaling out).
The Basics of System Scaling
Before diving 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 scaling is essentially the process of considering an increase in load and traffic on an existing infrastructure and ensuring a simple and non-complicated expansion of resources and performance.
It is critical to efficiently support the growing demand, especially with limited hardware resources. This necessitates the installation of more or better machines. It also involves enterprise software upgrades, which ensure better UX and agility and fewer maintenance costs.
The Two Primary Types of Scaling
There are two primary types of scaling: vertical and horizontal. While vertical scaling refers to the concept of “scaling up,” horizontal scaling means “scaling out.”
As we discuss the differences between these two types of scaling, you will see that the choice between these types will entirely depend on specific use cases and requirements. So, let’s learn more about vertical and horizontal scaling.
Diving Deep into Vertical Scaling (Scaling Up)
Let’s look at vertical scaling, its key characteristics, advantages, and disadvantages in greater detail.
Definition and Key Characteristics
Vertical scaling is essentially the process of enhancing the existing infrastructure to meet the rise in demand. Scaling up doesn’t require companies to alter their software application. This is because the same application is now executed on a much more powerful infrastructure.
Instead, vertical scaling involves scaling up memory, storage, and server capacity or replacing an outdated server with a new one.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 top benefits of vertical scaling:
- Simplicity of setup
With this type of scaling, a single node is responsible for handling the entire process. Since one node manages all the layers of the services, vertical scaling eliminates the need to synchronize and communicate with other servers to function. Moreover, the lack of complexity makes a vertically scaled infrastructure easier to maintain.
- Direct performance enhancement
Scaling up comes with direct performance enhancement because multi-core leads to scalability. Since all data is stored in a single machine, vertical scaling lessens the chances of data inconsistency. You can multiply the processing power by installing the latest generation of processors and servers.
- No need for code changes in some cases
Vertical scaling improves the overall infrastructure performance without having to add more processing units or hardware. This is also because there is minimal change to the web service code. In other words, we are increasing the capacity of the processor 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 computational capacity of the infrastructure. But, you can only enhance the processing power to the operating system limit, and the upgrades can be indefinite. You can only install the latest upgrades while catering to the machine’s RAM, storage, and processing power threshold.
- Downtime during upgrades
With vertical scaling, you are running the entire process using a single machine. This makes it difficult for you to frequently upgrade the system, as the upgrade process comes with considerable downtime. The downtime can be reduced by installing a backup server that can temporarily handle the operations and requests.
- Higher risk of a single point of failure
Since vertical scaling runs all the operations on a single server, you will 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 Horizontal Scaling (Scaling Out)
Now, let’s discuss horizontal scaling, its key characteristics, advantages, and disadvantages in detail.
Definition and Key Characteristics
Horizontal scaling refers to the idea of “scaling out.” 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 distribute the computational workload equally. Scaling out involves strategies like load balancing, clustering, and distributing file systems.
With this type of scaling, you’ll have the opportunity to enhance the I/O concurrency while reducing the load on existing nodes.
Advantages of Horizontal Scaling
This type of scaling has plenty of advantages. The top benefits include:
- Enhanced fault tolerance
Operations running on horizontal vs. vertical scaling tend to be more resilient and reliable. This is because the addition of more computational units to the infrastructure means the system doesn’t rely on one single node. Scaling out comes with enhanced fault tolerance because the operation is equally distributed among several nodes.
- Scalability beyond hardware limits
Remember: vertical scaling doesn’t allow scalability beyond the operating system’s capacity. With horizontal scaling, you can overcome this limitation by adding more computational units to the infrastructure. In other words, scaling becomes easier as we add more hardware to the current resource pool. You can upgrade the individual computational units, performing the most of vertical scaling at the same time.
- Load distribution
It is important for this type of scaling to facilitate load balancing and distribution to ensure effective traffic management for different machines. The idea is to put an equal load on each node and achieve an equal load distribution. The load distribution increases the system’s upgradability as scaling doesn’t result in downtime since we are no longer limited to a single unit’s capacity.
Disadvantages and Limitations
As with vertical scaling, there are some disadvantages to this type of scaling include:
- Complexity in setup and maintenance
It’s common to experience complexity in maintenance and setup with horizontal scaling. This is because you are adding more operating units or nodes to the infrastructure. Besides the hardware upgrades, you may need to add additional software resources for load balancing and virtualization. At the same time, you’d need to ensure effective node synchronization to facilitate seamless communication.
- Potential data consistency issues
Since each node of the horizontally scaled system caters to different requests, data sharing and communication are often out of sync. This results in data inconsistency, which should be addressed immediately to ensure efficient processing and operation.
- Requirement for load balancing
Ideally, the added hardware will have equal computational capacity. If not, the scaling will have to facilitate a load balancer to spread the traffic among all the nodes. With load balancing, you must ensure the system doesn’t go down if one of the nodes fails to function.
Horizontal and Vertical Scaling: A Side-by-Side Comparison
Here are the top three 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 go for vertical scaling because an increasing number of powerful multi-core machines are now packaged in a single box. In other words, you can achieve 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 wouldn’t be an ideal choice because running the application on multiple machines might even degrade its quality.
Simply upgrading the hardware (vertical scaling) could help meet the growing demand. However, horizontal is more reliable than vertical scaling because it involves multiple machines that can share the computational workload.
Scalability Potential
Long-term scalability or upgradability is a major factor differentiating horizontal and vertical scaling. Horizontal scaling allows a continuous upgrade process that, unlike vertical scaling, doesn’t require bringing the entire system down.
Real-world Use Cases and Industry Examples
Let’s discuss some use cases of the two scaling options to help you determine which is the right scaling model for your business.
Successful Vertical Scaling Implementations
Vertical scaling is a good option for newer companies because they are still in the early phases of building traffic and a user base. This is also useful for companies that are planning for fewer upgrades.
Scaling up is suitable if increasing the machine’s 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 Horizontal Scaling Implementations
Horizontal scaling is the better choice for companies that want to upgrade quickly and frequently without causing significant downtime. Scaling out helps reduce single points of failure.
Most importantly, horizontal scaling is advisable for companies using a microservices architecture and those that have enough 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’s important for companies to specify their computational workload requirements to make a solid decision when scaling.
FAQ
What does it mean to scale a system?
Scale 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 the machine capacity results in better performance. Companies that have just started out should use vertical scaling, especially if they want to offer few-and-far-between upgrades.
How does horizontal scaling enhance fault tolerance?
Since horizontal scaling ensures more than one server sharing the computational workload, a fault in any one of the servers will not result in downtime because others are ready for backup.
Are there cost benefits to one scaling method over the other?
Vertical scaling is more cost-effective than horizontal scaling because scaling out involves higher upfront hardware expenses, licensing fees, and utility costs and requires re-architecting the software system.
Can a system utilize both vertical and horizontal scaling simultaneously?
Companies should aim to move between horizontal and vertical scaling. It allows them to benefit from both paradigms. For instance, teams can modify their existing pool of machines using memory upgrades by installing multiple RAMs in a system while planning to increase the capacity of each of the installed RAMs.
