Azure Cloud Zero #12: Load Balancing and Scale Sets for VMs and Networking

In the previous article, we discussed how to configure virtual machines (VMs) and set up virtual networks and subnets. Now, we’ll delve deeper into creating load balancers and scale sets in Azure. Load balancers efficiently distribute incoming network traffic across multiple VMs, while scale sets enable horizontal scaling of VMs—enhancing application availability and fault tolerance.

Introduction to Load Balancers

In Azure, a load balancer is a networking service that distributes incoming network traffic across multiple virtual machines (VMs), thereby improving application availability and fault tolerance. Azure load balancers can be either public or internal:

• Public Load Balancer: Used for applications exposed to the Internet.
• Internal Load Balancer: Used to balance traffic within an Azure virtual network.

Creating a Public Load Balancer

Below are the basic steps to create a public load balancer:

1. Create the Load Balancer:
   Use the Azure portal or Azure CLI to create the load balancer.

   Azure CLI command:

   az network lb create \
     --resource-group MyResourceGroup \
     --name MyLoadBalancer \
     --sku Standard \
     --public-ip-address MyPublicIP \
     --frontend-ip-configuration MyFrontendConfig
   

   This command creates a public load balancer named MyLoadBalancer.

2. Configure Load Balancing Rules:
   Load balancing rules define how traffic is distributed.

   az network lb rule create \
     --resource-group MyResourceGroup \
     --lb-name MyLoadBalancer \
     --name MyLoadBalancingRule \
     --frontend-ip-configuration MyFrontendConfig \
     --backend-pool-name MyBackendPool \
     --protocol Tcp \
     --frontend-port 80 \
     --backend-port 80
   

3. Add a Backend Pool:
   A backend pool is a group of VMs associated with the load balancer.

az network lb backend-pool create \
  --resource-group MyResourceGroup \
  --lb-name MyLoadBalancer \
  --name MyBackendPool

az network lb set-inbound-nat-rule \
  --resource-group MyResourceGroup \
  --lb-name MyLoadBalancer \
  --backend-pool-name MyBackendPool \
  --vm-id <VM_ID>

Practical Example: Using a Load Balancer

Suppose we have a web application that must remain highly available during traffic surges. By deploying a public load balancer, we can distribute user requests across multiple web-tier VMs—ensuring continued service even if one VM fails. For instance, consider three VMs with private IP addresses 10.0.0.4, 10.0.0.5, and 10.0.0.6. All external traffic flows through the load balancer’s public IP address. When users access the application, the load balancer routes each request to one of these three VMs according to the configured distribution rules.

Introduction to Scale Sets

A scale set is an Azure service that enables parallel management of a group of identical VMs. It simplifies and automates scaling—both scaling out (adding VMs) and scaling in (removing VMs)—to meet changing workload demands.

Creating a Scale Set

Below are the basic steps to create a scale set:

1. Define the Scale Set:
   Create a scale set to manage a group of VMs.

   az vmss create \
     --resource-group MyResourceGroup \
     --name MyScaleSet \
     --image UbuntuLTS \
     --vm-sku Standard_DS1_v2 \
     --instance-count 2 \
     --upgrade-policy-mode Automatic
   

2. Configure Load Balancing:
   A load balancer is automatically configured when the scale set is created.

3. Scale Out or In:
   Adjust the number of VM instances with a single command.

   az vmss scale \
     --resource-group MyResourceGroup \
     --name MyScaleSet \
     --new-capacity 5
   

Practical Example: Using a Scale Set

Suppose our application has launched successfully and user traffic is steadily increasing. We can use the scale set to rapidly increase capacity—from 2 to 5 VM instances—using the command above. Azure automatically provisions the additional resources, and the integrated load balancer continues routing traffic evenly across all instances.

Summary

In this tutorial, we covered how to create and configure both load balancers and scale sets on the Azure cloud platform. Together, these services significantly enhance VM availability, scalability, and resilience—providing a robust infrastructure foundation for modern applications. In the next article, we’ll explore Azure storage services in depth, with a focus on using Azure Blob Storage.