Scaling is an important aspect of managing systems and applications. Providers of systems, applications, and services experience an increase in user demand and consequently need to manage application and service demand without decreasing performance quality or taking the risk of system failure. There are a few ways this can be accomplished, the most common being horizontal scaling and vertical scaling. Horizontal scaling is when more machines are added to share the load. Vertical scaling is when a service provider adds more capability to their current machine to manage demand, while handling the increase usage of the volume. In this blog, you will understand what horizontal and vertical scaling are, along with their differences in detail.
Table of Contents:
What is Horizontal Scaling?
Horizontal scaling is the process of adding more computers or servers to your system to perform more work. It simply adds machines that share the workload instead of boosting one machine’s capacity. This approach is also referred as scale-out.
Example: If a store gets more customers, it can open more branches in different areas to serve more customers.
What is Vertical Scaling?
Vertical scaling refers to upgrading the existing machine to make it more capable. That could be as simple as adding more memory (RAM), a faster processor (CPU), or larger storage. This is also termed scale-up.
Example: If a restaurant gets more customers, it hires more staff and adds additional seating instead of opening a new location.
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Horizontal Scaling vs Vertical Scaling
| Feature |
Horizontal Scaling |
Vertical Scaling |
| Approach |
It is the process of adding more machines. |
It is the process of upgrading the same machine. |
| Cost |
It can become expensive in the long term because more hardware and maintenance are required. |
It has a lower initial cost but frequent upgrades can make it costly. |
| Downtime |
Usually there is no downtime if it is implemented properly. |
It may require downtime during hardware upgrades. |
| Performance Limit |
It can handle very large workloads as more machines are added. |
It is limited by the maximum capacity of a single machine. |
| Maintenance |
It is more complex because multiple systems need to be managed. |
It is easier to maintain since only one system is involved. |
| Fault Tolerance |
It offers high fault tolerance because if one machine fails the others keep working. |
It has low fault tolerance because failure of the single machine can stop the entire system. |
| Scalability |
It is highly scalable since more machines can be added whenever needed. |
It has limited scalability because the capacity of one machine cannot increase indefinitely. |
| Implementation Complexity |
It is more complex because it requires distributed systems and proper configuration. |
It is simple to implement because only hardware upgrades are needed. |
Key Features of Horizontal and Vertical Scaling
Let’s explore the features of horizontal and vertical scaling:
Horizontal Scaling
- Distribution of workloads: It distributes work to many machines.
- Scalability: It is highly scalable with growth possibilities.
- Load Balancing: It uses a load balancer to share the job evenly.
- Best Use Case: High-traffic web applications, streaming services, and online games.
Vertical Scaling
- Performance Boosts: Accelerates the speed and capacity of one machine.
- Easy Set-up: Doesn’t require several machines.
- Hardware Limitation: It is possible only to a certain level of upgrade.
- Recommended Application: Local web servers or small businesses, or single-database systems
Benefits and Challenges of Horizontal Scaling
Let’s explore some of the benefits and challenges related to horizontal scaling:
Benefits of Horizontal Scaling
- High Capacity: It can quickly accommodate increased traffic.
- Fault Tolerance: If one machine goes down, there are other machines ready to take over.
- Flexibility: It is easy to add more machines when demand spikes.
- Improved Performance: Workload can be distributed across multiple machines, reducing bottlenecks.
Challenges of Horizontal Scaling
- Complex Setup: It requires special configuration and additional software to implement.
- Increased Cost: More machines mean more space and maintenance costs.
- Compatibility: Application needs to remain compatible with multiple systems.
- Network Overhead: Communication between machines can create latency issues.
Benefits and Challenges of Vertical Scaling
Let’s explore some benefits and challenges related to vertical scaling:
Benefits of Vertical Scaling
- Easy: Easy to set up, requiring no application changes or major configurations.
- Fast Upgrade: Upgrading by adding hardware is much faster.
- Low Complexity: There is only one machine to deal with.
- High Performance: A single powerful machine can deliver strong performance without distributing workloads.
Challenges of Vertical Scaling
- Upgrade Limitation: Each machine has a maximum upgrade capacity.
- Downtime Risk: Upgrades always stop services temporarily.
- Single Point of Failure: If that machine fails, the whole system goes down.
- High-End Hardware Cost: Powerful servers and components can become very expensive.
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Security & Reliability Considerations
When planning the strategies for scaling, it is important to consider the impact on the system security and overall reliability.
- Horizontal Scaling: With more machines, it logically follows that there are more network connections to secure on each machine. Regularly distributed backups will be required.
- Vertical Scaling: Security is easier to accomplish in this scenario, but it is at risk for a single point of failure and compromise of the machine. If the machine gets hacked or physically damaged, then you can be compromised.
- Both Types of Scaling: Must include monitoring tools, firewalls, and proper data protection methods.
When to Choose Horizontal Scaling vs Vertical Scaling
Choose Horizontal Scaling When:
- Your application is serving millions of users.
- You expect growth to continue.
- You need high availability with no downtime.
- Your application is designed to work across multiple machines.
- You require better fault tolerance so one machine’s failure doesn’t affect the entire system.
Choose Vertical Scaling When:
- You have a small to medium workload.
- Your system can support more users simply by upgrading hardware.
- You would like to keep the setup simple and cheap.
- Your application is not built for distributed systems.
- You want quick performance improvements without major changes.
Common Mistakes in Choosing a Scaling Strategy
- Insufficient Future Planning: Selecting vertical scaling without recognizing how soon hardware limits may be reached in the future.
- Poor Technical Readiness: Applying horizontal scaling without having the technology/software/load balancer in place.
- Overlooking Security Requirements: Ignoring additional security needed when managing multiple machines when using horizontal scaling.
- Without a Maintenance Budget: Failing to set a budget for ongoing maintenance, updates to hardware, or other system support.
- Scaling Prematurely: Increasing capacity before demand exists, resulting in wasted costs and idle resources.
Conclusion
Horizontal scaling and vertical scaling are both effective methods for increasing system performance, but they function in different ways. Horizontal scaling uses more machines and servers to share the workload, enabling growth and is limited only by budget and operational designs, and improves fault tolerance. Vertical scaling increases the performance of a single machine by upgrading its hardware, mostly CPU, RAM, or storage. Choosing the best option depends on factors such as business requirements, budget, technical expertise, and expectations for future growth. In a rapid scaling situation, it is important to select the most appropriate scaling option to ensure efficient performance, cost-effectiveness, and usability for current and future needs.
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Horizontal Scaling vs Vertical Scaling – FAQs
Q1. What is horizontal and vertical scaling in system design?
Horizontal and vertical scaling help manage growth by adding machines or upgrading one machine.
Q2. Which is more cost effective in horizontal and vertical scaling?
Vertical scaling is cheaper initially while horizontal scaling costs more over time.
Q3. How does performance differ in horizontal and vertical scaling?
Horizontal scaling shares workload across machines while vertical scaling boosts a single machine.
Q4. What are the security risks in horizontal and vertical scaling?
Horizontal scaling increases network security needs while vertical scaling risks single point failure.
Q5. When should I use horizontal and vertical scaling?
Choose horizontal scaling for growth and vertical scaling for simplicity.
Q6. What is the main difference in horizontal scaling vs vertical scaling?
The difference between horizontal scaling and vertical scaling is that horizontal adds more machines while vertical upgrades the same machine.