Load Balancing: Definition
Modern websites and applications generate lots of traffic and serve numerous client requests simultaneously. Load balancing helps meet these requests and keeps the website and application response fast and reliable.
What is load balancing?
Load balancing is a core networking solution used to distribute traffic across multiple servers in a server farm. Load balancers improve application availability and responsiveness and prevent server overload. Each load balancer sits between client devices and backend servers, receiving and then distributing incoming requests to any available server capable of fulfilling them.
How does it work?
Load balancing is handled by a tool or application called a load balancer. It can be either hardware-based or software-based. Hardware load balancers require the installation of a dedicated load balancing device; software-based load balancers can run on a server, on a virtual machine, or in the cloud. Content delivery networks (CDN) often include load balancing features.
When a request arrives from a user, the load balancer assigns the request to a given server, and this process repeats for each request. Load balancers determine which server should handle each request based on several different algorithms. These algorithms fall into two main categories: static and dynamic.
Where is load balancing used?
As discussed above, load balancing is often used with web applications. Software-based and cloud-based load balancers help distribute Internet traffic evenly between servers that host the application. Some cloud load balancing products can balance Internet traffic loads across servers that are spread out around the world, a process known as global server load balancing (GSLB).
It is also commonly used within large localized networks, like those within a data center or a large office complex. Traditionally, this has required the use of hardware appliances such as an application delivery controller (ADC) or a dedicated load balancing device. Software-based load balancers are also used for this purpose.
Why is it important?
It is essential to maintain the information flow between the server and user devices used to access the website (e.g., computers, tablets, smartphones).
There are several benefits:
- Reliability: A website or app must provide a good UX even when traffic is high. Load balancers handle traffic spikes by moving data efficiently, optimizing application delivery resource usage, and preventing server overloads. That way, the website performance stays high, and users remain satisfied.
- Availability: It is important because it involves periodic health checks between the load balancer and the host machines to ensure they receive requests. If one of the host machines is down, the load balancer redirects the request to other available devices. It also removes faulty servers from the pool until the issue is resolved. Some load balancers even create new virtualized application servers to meet an increased number of requests.
- Security: Load balancing is becoming a requirement in most modern applications, especially with the added security features as cloud computing evolves. The load balancer’s off-loading function protects from DDoS attacks by shifting attack traffic to a public cloud provider instead of the corporate server.
- Predictive Insight: Load balancing includes analytics that can predict traffic bottlenecks and allow organizations to prevent them. Predictive insights boost automation and help organizations make decisions for the future.
What Load Balancer Types Exist?
Load balancers vary in storage type, balancer complexity, and functionality. The different types of load balancers are explained below.
- Hardware Load Balancer: As the name implies, relies on physical, on-premises hardware to distribute the application and network traffic. These devices can handle a large volume of traffic but often carry a hefty price tag and are fairly limited in terms of flexibility.
- Software Load Balancer: It comes in two forms – commercial or open-source – and must be installed before use. Like cloud-based balancers, these tend to be more affordable than hardware solutions.
- Virtual Load Balancer: It differs from software load balancers because it deploys the software of a hardware load balancing device on a virtual machine.
- Cloud-Based: Cloud-based load balancing utilizes cloud infrastructure. Some examples of cloud-based load balancing are Network Load Balancing, HTTP(S) Load Balancing, and Internal Load Balancing.
Now you know what load balancing is, and how it enhances server performance and security and improves the user experience. The different algorithms and load balancing types are suited for different situations and use cases, and you should be able to choose the right load balancer type for your use case.