Servers play a huge role in centralizing information. The number of individuals accessing a server within a particular time can be high, and therefore, it is important to control how information is accessed or else the servers will crash. Contrary to popular belief, a server is not a device, but rather, it is the program that has been installed in a computer to manage the delivery of service to other computers that try to access the centralized information. Servers may be dedicated, such that they are specifically meant to offer services to other computers, or they may also be used for more than one purpose.
What is Server Load Balancing
The users accessing a server generate traffic, and this is what is referred to as the load. The load is usually distributed over many servers, which make up the server pool. The number of requests sent to a server within a second can be very high. Such a situation requires that the server performs optimally. In order to successfully meet the high demand of client requests in a cost-effective manner, it is suitable to use many servers at once. Otherwise, access to information will be slowed down as the server will be overworked.
Load balancers act as the client requests. They are designed to direct each request to any server that will fulfill it as fast as possible. In case a particular server goes offline, then the load balancer starts redirecting traffic to the other servers that are still active. When a new server is added to the pool, the load balancer immediately starts sending requests to it. Therefore, the load balancer fulfills three primary functions.
Server Load Balancing Software
- Ensures that reliability is achieved by sending requests to online servers only.
- It ensures efficient network load distribution over the server pool.
- It ensures flexibility is achieved as it is possible to add or reduce the number of servers efficiently.
In the past, load balancers were offered as hardware devices (Application Delivery Controllers). However, using ADC's in today’s technological infrastructure is expensive, and not easy to install. Software load balancers on the other hand help to cut down on cost and are flexible. Some advantages of software load balancers include.
- There is no need to wait for a specific hardware to be installed and configured. It is easy to scale-up or down at any time.
- Clients will get value for money as there is no capping or increased payment for high traffic.
- A software load balancer can cut down on more than 75% of the operational costs.
- One software can be used for containers, cloud, and bare metal. Additionally, it makes app deployment easy.
It is a multi-threading and dynamic load balancer. It has a fast packet processing capability and can be integrated with different data center networks making it suitable for hosting companies, network operators, and telecom companies.
It is suitable for web servers due to its high security, performance, and reliability. It works by dividing traffic between different servers. Afterwards, it continually monitors the servers to ensure that they are always online before beginning to send requests.
Server Load Balancing Algorithms
A suitable load balancing algorithm should be able to decide the suitable server pool to which a request should be directed. Algorithms fall under either the network or application layer. The right algorithm will affect the success and overall performance of an enterprise. Selection of a suitable algorithm should be based on unpredictable or predictable scenarios.
Network Layer Algorithms
- Round Robin- a server pool is programmed such that it can handle client requests in a rotating manner.
- Weighted round robin- a server is rated depending on the number of requests it is able to fulfill.
- Least Connections- a request will be forwarded to the server that has fewest connections.
Application Layer Algorithms
- Accurate Load Distribution- It selects the most suitable server that can process an algorithm in the shortest possible time.
- Request Specific Distribution- It routes requests to less busy servers since the processing time between requests frequently differs.
Hardware vs Software load balancer
In the past, load balancing was specifically undertaken by hardware devices. However, software is nowadays taking over the functions of load balancing and the primary difference between these two is determined by the labor that will go into the platform development.
Hardware load balancers are more versatile as they support different server counts, throughput, and connectivity features. Additionally, they have integrated circuits that help to improve handling of data. Software load balancers may lack features such as authentication integration, Active directory, and SSL Hardware Accelerators. However, selecting a load balancer should be determined by specific business needs.