As you build your infrastructure to support your growing company, you may be confused by the terms “horizontal scaling” and “vertical scaling” and how they apply to your business. Which is better when it comes to horizontal vs. vertical scaling? What is the best way for you to scale up? Let’s start with some terminology.
What is Scalability?
Scalability describes a business’ ability to grow or shrink. Usually, scalability implies growth but a business can scale up or down if circumstances require. For instance, a retail business may need to scale up during the holiday season, then scale down afterward.
Scalability is similar to a rubber band, able to move quickly to get larger or smaller. Therefore, your company can scale up, scale down, or scale out.
Online businesses require quantities of traffic to become successful. Whether your business has a website, application, web service, or subscription, it can be difficult to predict the level of traffic you will incur. This is especially true when you are just getting started. If you aren’t prepared for a lot of traffic, your system might crash which doesn’t make a very good impression on your customers.
Scalability describes how adaptable your business is, so when you need to meet a higher demand, you are ready. This way, customers can be assured of continuous high-quality service.
What is Horizontal Scaling?
Horizontal scaling also called scaling out, refers to increasing the number of nodes you have on a virtual network or servers on a physical network. In other words, if your application is too big to run on your current server(s), then you need to upgrade by adding more capacity. This means adding servers or nodes depending on where it’s hosted.
A good analogy is when one person on a team suddenly gets overwhelmed with work, other team members can step in to spread out the work.
What is Vertical Scaling?
Vertical scaling also called scaling up, describes the addition of resources to a system to enable it to meet demand. How does this differ from scaling out?
Horizontal scaling implies adding nodes, but vertical scaling describes adding power to your existing machine. Therefore, vertical scaling would upgrade the CPUs to provide higher processing power. You can vertically scale any of your processing including the storage, memory, or network speed. Or replacing an old server with an upgraded model.
Horizontal vs. Vertical Scaling
Which type of scaling is better?
As a reminder, horizontal scaling requires you to rework the implementation of layers of your services. Let’s look at a three-tier architecture.
What Does Three-Tier Architecture Mean?
A three-tier architecture is a client-server architecture in which the functional process logic, data access, computer data storage and user interface are developed and maintained as independent modules on separate platforms.
Three-tier architecture is a software design pattern and a well-established software architecture.
With a three-tier architecture, you have a presentation tier (user interface/client), logic tier (virtual server/services), and data tier (storage/databases). For the purpose of horizontal scaling, each tier or their functions can be assigned to a unique node.
It’s possible that while you’re running each tier on a separate server, one of the servers is not performing well, not up to par with the other servers. In this case, you can scale the server up or out. You can upgrade it with more resources or add a new server to take some of the workload.
It’s a difference between buying new resources (horizontal scaling) or improving or modifying existing resources (vertical scaling).
Advantages of Horizontal Scaling
- Scaling is easier on the hardware side – All you need to do is to add more machines to your existing pool. You don’t need to decide which machine or system you need to upgrade when you choose scaling horizontally.
- Less downtime – You don’t have to switch off the old machine to replace it, since you’re just adding a new one in addition to what you currently have.
- Better resilience and fault tolerance – When you rely on a single node for your operations, you are at a higher risk of losing it when the node fails. Distributing it out safeguards against loss.
- Better performance capacity – Horizontal scaling results in more endpoints to connect which provides a better performance.
Disadvantages of Horizontal Scaling
- Increasing complexity of operation and maintenance – It’s easier to maintain a single server than multiple servers. You will also need load balancing software and backups become more complex. You may also need virtualization. It’s important to confirm that nodes are synchronized and communicate effectively.
- Higher initial costs – When you add a new server, you pay more than you would upgrading one you already own.
Advantages of Vertical Scaling
- Cost-effective – It’s cheaper to upgrade an existing server than add a new one. When scaling vertically you’re less likely to need new backup and virtualization software. Maintenance costs remain relatively the same.
- Less complex communication – Using a single node to handle all the layers of your services, there is no need to communicate with other machines to work properly. You may also have faster responses.
- Maintenance is simpler – Maintenance is cheaper and less complex because you have a small number of nodes.
- Low-quantity of software changes – Changing how the software works or is implemented on a server is less likely.
Disadvantages of Vertical Scaling
- Increased potential downtime – When upgrading you’ll need to take the system down unless you have adequate backup server.
- HIgher risk of loss – With all of your operations on a single server, loss is a higher risk if a failure should occur.
- Upgrade limitations – You can only upgrade a machine so many times before you need to replace it. There is always a threshold for processing power, storage, and RAM.
Which Should You Choose and When?
Think About Long-Term Viability
The best way to decide is to think about what’s best for your company’s long-term viability. Since there’s no one-size-fits-all solution, it’s a best practice to examine these key factors:
- Cost
- Future-proofing
- Topographic distribution – Where your clients are geographically
- Reliability
- Future upgrades and flexibility
- Performance and complexity
Why Scaling Out is Better than Up
Horizontal scaling is more desirable than vertical scaling in almost every situation. You are never caught in resource deficit. When you’re ready to increase capacity, your system stays online with your current pool of computer resources while you go about adding more.
Horizontal scaling up offers elasticity.
How to Achieve Effective Horizontal Scaling
Follow these best practices for optimal horizontal scaling.
- Make your application stateless on the server side as much as you can.
- Develop your app with a service-oriented architecture for cost-effectiveness.
Enjoy the Best of Both Solutions
This job of scaling up or out doesn’t have to be all or nothing. You can do both. Start by splitting out parts of your application with the highest load into microservices so you can scale them out. Then you can scale up the original app when demand spikes, but probably not as far as you would have needed if you were only scaling up.
What is Cloud Scalability?
Cloud scalability or auto-scaling is a cloud computing feature that allows users to automatically scale cloud services, like virtual machines (VM) and server capacities, up or down, depending on defined situations.
Cloud scalability offers seamless increases and decreases during usage fluctuations to maintain performance.
On-Premise vs. Cloud Scaling
Cloud scaling works similar to on-premise scaling. A cloud service provider (CSP) can implement hyper-convrged infrastructure-based horizontal scaling or use virtual distributed services. For companies with private or hybrid cloud solutions, the hyper-converged infrastructure-based solution is commonly used. This reduces the time you need to worry about computer hardware.
Both Azure and AWS, cloud service providers, have automatic scaling. This makes scaling cost-effective and efficient. This is one plus of cloud migration.
Cost: Scale Up or Scale Out?
There are three key factors to keep in mind while deciding on the best scaling solution for your company.
1. Performance
Horizontal scaling gives you the ability to combine the computing strength of multiple servers into one resource pool. This is a powerful tool that will drive drastic improvement in performance. But if your scaling needs can be solved with one machine, vertical scaling may be the right choice for now.
2. Flexibility
Flexibility is important to make costs and performance efficient. Vertical scaling is less flexible since you’re bound by the capability of your one machine. Scaling out gives you the ability to access servers when you need more power because requirements flucuate. That is a much more flexible solution.
3. Cost
Ultimately, everything comes down to cost. Horizontal scaling requires adding more servers to your existing infrastructure for a better performance. This can be very expensive. Since vertical scaling is using only one machine, it is usually the more cost-effective option.
Interested in Finding Out More about Scalability?
If you want to find out more about scaling up or out, contact us.