What Is Server Load Balancing?

There are many definitions of Server Load Balancing (SLB). One good way to think about SLB is as a way to distribute traffic across multiple servers so that the load (incoming requests) is shared across these servers and no one server ends up with too much to do!

The load balancer intercepts the incoming traffic and shares it across the available servers. By doing this the load balancer enables multiple servers to respond as if they were a single device or server. This in turn means that more simultaneous requests can be handled. The number of servers that sit behind the load balancer can be anything from 2 (minimum) to hundreds. The load balancing process is completely transparent to any users (using a website for example).

There are additional benefits to server load balancing. First becasue the load is distributed across multiple servers the service being provided can be highly available. That is if one of the servers break down the load can still be handled by the other servers. A second benefit is scalability. This means that if the load increases substantially more servers can be added behind the load balancer in order to cope with the increased load.

Also note that server load balancing can be achieved using either software running on a server or via dedicated hardware servers.