Understanding NLB between WFE and App Servers

Question

There are two WFEs with high availability. I asked someone if you are using NLB between them to load balance and he said yes.

Then he said we also have two app servers with high availability. I asked if you are also using NLB for them? He said no and he further said servers are not load balanced but only service applications. (what ever that means)

So what I gathered from it:

1. You need NLB to load balance WFEs
2. But you don't need NLB to load balance app servers because it is done by SharePoint itself.

Is my understanding correct?

Answer 1

You're mostly correct on both counts. You need a load balancing solution of some sort to distribute traffic between SharePoint web servers that are hosting content web applications accessed by end users. Windows Network Load Balancing (NLB) is one option you can use to provide that, but there are other options as well. NLB is a software-based load balancer, but you can also use hardware-based load balancers such as appliances from F5 or Cisco to distribute that load.

In SharePoint 2010 and 2013, you don't need to provide a load balancing solution for service applications. Microsoft has built a simple round-robin load balancer into its Service Application Framework that distributes traffic across each application server automatically. It's not sophisticated, and you have no control over its configuration or implementation, but it's built-in and it works.

John