Load Balancers

Overview

Millions of requests could arrive per second in a typical data center. To serve these requests, thousands (or a hundred thousand) servers work together to share the load of incoming requests.

Note: Here, it’s important that we consider how the incoming requests will be divided among all the available servers.

A load balancer (LB) is the answer to our problem. The job of the load balancer is to fairly divide all client requests among the pool of available servers. Load balancers perform this job to avoid overloading or crashing servers.

The load balancing layer is the first point of contact within a data center after the firewall. A load balancer may not be required if a service entertains a few hundred or even a few thousand requests per second. However, for increasing client requests, load balancers provide the following capabilities:

• Scalability: By adding servers, the capacity of the application/service can be increased seamlessly. Load balancers make such upscaling or downscaling transparent to the end users.
• Availability: Even if some servers go down or suffer a fault, the system still remains available. One of the jobs of load balancers is to hide the faults and failures of the servers.
• Performance: Load balancers can forward requests to servers with a lesser load so the user can get a quicker response time. This not only improves performance but also improves resource utilization.

Here’s an abstract depiction of how load balancers work: