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Azure Virtual Machine Scale Sets

Virtual Machine Scale Sets (VMSS) let you create and manage a group of identical, load‑balanced VMs. Scale sets provide high availability, auto‑scaling, and integrated health monitoring.

Key Features

• Automatic scaling based on metrics or schedules.
• Integration with Azure Load Balancer and Application Gateway.
• Support for Windows and Linux images.
• Custom VM extensions and scripts.
• Rolling upgrades with health checks.

Getting Started

Use the Azure portal, Azure CLI, or ARM templates to create a scale set.

Azure CLI Example

az vmss create \
  --resource-group MyResourceGroup \
  --name MyScaleSet \
  --image UbuntuLTS \
  --upgrade-policy-mode automatic \
  --admin-username azureuser \
  --generate-ssh-keys \
  --instance-count 2 \
  --vm-sku Standard_DS2_v2

ARM Template Snippet

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Compute/virtualMachineScaleSets",
      "apiVersion": "2022-08-01",
      "name": "myScaleSet",
      "location": "[resourceGroup().location]",
      "properties": {
        "upgradePolicy": { "mode": "Automatic" },
        "virtualMachineProfile": {
          "storageProfile": {
            "imageReference": {
              "publisher": "Canonical",
              "offer": "UbuntuServer",
              "sku": "18.04-LTS",
              "version": "latest"
            }
          },
          "osProfile": {
            "computerNamePrefix": "vmss",
            "adminUsername": "azureuser",
            "linuxConfiguration": { "disablePasswordAuthentication": true }
          },
          "networkProfile": {
            "networkInterfaceConfigurations": [
              {
                "name": "nicConfig",
                "properties": {
                  "primary": true,
                  "ipConfigurations": [
                    {
                      "name": "ipConfig",
                      "properties": {
                        "subnet": { "id": "[resourceId('Microsoft.Network/virtualNetworks/subnets', 'myVnet', 'default')]" }
                      }
                    }
                  ]
                }
              }
            ]
          }
        },
        "sku": {
          "name": "Standard_DS2_v2",
          "capacity": 2,
          "tier": "Standard"
        }
      }
    }
  ]
}

Scaling Configuration

Common Tasks

• Perform rolling upgrades
• Monitor health and metrics
• Add custom extensions

FAQs