Azure Spot VMs for cost savings - Commands & Configuration

Introduction

Sometimes cloud servers cost a lot. Azure Spot VMs let you use spare servers at a lower price. They can be taken back by Azure anytime, so they are good for tasks that can pause and restart.

When running batch jobs that can stop and start without problems.

When testing software that does not need to run all the time.

When you want to save money on virtual machines for flexible workloads.

When running background tasks that can be interrupted and resumed later.

When you want to try cloud servers at a lower cost before buying full-price ones.

Config File - azuredeploy.json

azuredeploy.json

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "vmName": {
      "type": "string",
      "defaultValue": "spot-vm-example",
      "metadata": {
        "description": "Name of the virtual machine"
      }
    },
    "adminUsername": {
      "type": "string",
      "defaultValue": "azureuser",
      "metadata": {
        "description": "Admin username for the VM"
      }
    },
    "adminPassword": {
      "type": "securestring",
      "metadata": {
        "description": "Admin password for the VM"
      }
    }
  },
  "resources": [
    {
      "type": "Microsoft.Compute/virtualMachines",
      "apiVersion": "2022-08-01",
      "name": "[parameters('vmName')]",
      "location": "eastus",
      "properties": {
        "priority": "Spot",
        "evictionPolicy": "Deallocate",
        "billingProfile": {
          "maxPrice": -1
        },
        "hardwareProfile": {
          "vmSize": "Standard_DS1_v2"
        },
        "storageProfile": {
          "imageReference": {
            "publisher": "Canonical",
            "offer": "UbuntuServer",
            "sku": "18.04-LTS",
            "version": "latest"
          },
          "osDisk": {
            "createOption": "FromImage"
          }
        },
        "osProfile": {
          "computerName": "[parameters('vmName')]",
          "adminUsername": "[parameters('adminUsername')]",
          "adminPassword": "[parameters('adminPassword')]"
        },
        "networkProfile": {
          "networkInterfaces": [
            {
              "id": "[resourceId('Microsoft.Network/networkInterfaces', concat(parameters('vmName'), '-nic'))]"
            }
          ]
        }
      }
    },
    {
      "type": "Microsoft.Network/networkInterfaces",
      "apiVersion": "2022-07-01",
      "name": "[concat(parameters('vmName'), '-nic')]",
      "location": "eastus",
      "properties": {
        "ipConfigurations": [
          {
            "name": "ipconfig1",
            "properties": {
              "subnet": {
                "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Network/virtualNetworks/myVnet/subnets/default"
              },
              "privateIPAllocationMethod": "Dynamic"
            }
          }
        ]
      }
    }
  ]
}

This ARM template creates an Azure Spot VM named 'spot-vm-example' in the East US region.

priority: Set to 'Spot' to use spare capacity at a lower cost.

evictionPolicy: 'Deallocate' means the VM is stopped but not deleted if Azure reclaims it.

billingProfile.maxPrice: -1 means pay up to the regular price, but usually cheaper.

The VM uses Ubuntu 18.04 LTS and a standard DS1_v2 size.

A network interface is created and attached to the VM in an existing virtual network subnet.

Commands

Create a resource group to hold all related Azure resources in the East US region.

Terminal

az group create --name myResourceGroup --location eastus

Expected Output

{

  "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup",

  "location": "eastus",

  "managedBy": null,

  "name": "myResourceGroup",

  "properties": {

    "provisioningState": "Succeeded"

  },

  "tags": {},

  "type": "Microsoft.Resources/resourceGroups"

}

→

--name - Sets the name of the resource group

→

--location - Sets the Azure region for the resource group

Deploy the ARM template to create the Spot VM with the given admin password.

Terminal

az deployment group create --resource-group myResourceGroup --template-file azuredeploy.json --parameters adminPassword=MyStrongP@ssw0rd

Expected Output

{

  "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myResourceGroup/providers/Microsoft.Resources/deployments/azuredeploy",

  "name": "azuredeploy",

  "properties": {

    "provisioningState": "Succeeded",

    "outputs": {}

  }

}

→

--resource-group - Specifies the resource group to deploy into

→

--template-file - Points to the ARM template file

→

--parameters - Passes parameters like admin password securely

Check the current status of the Spot VM to confirm it is running.

Terminal

az vm get-instance-view --resource-group myResourceGroup --name spot-vm-example --query instanceView.statuses[1]

Expected Output

{

  "code": "PowerState/running",

  "displayStatus": "VM running",

  "level": "Info",

  "time": null

}

→

--resource-group - Specifies the resource group of the VM

→

--name - Specifies the VM name

→

--query - Filters output to show VM power state

Key Concept

If you remember nothing else from this pattern, remember: Azure Spot VMs let you save money by using spare capacity that can be taken back anytime, so use them only for flexible, interruptible workloads.

Common Mistakes

Trying to use Spot VMs for critical apps that must run all the time.

Spot VMs can be evicted by Azure at any time, causing downtime.

Use Spot VMs only for workloads that can handle interruptions and restart later.

Not setting evictionPolicy or maxPrice in the VM configuration.

Without evictionPolicy, the VM may be deleted instead of deallocated, losing data. Without maxPrice, costs may be unpredictable.

Set evictionPolicy to 'Deallocate' and maxPrice to -1 or a specific value to control eviction and cost.

Deploying Spot VMs in regions or sizes with no available spare capacity.

The deployment will fail or the VM will not start because no Spot capacity is available.

Check Azure Spot VM availability for your region and VM size before deploying.

Summary

Create a resource group to organize Azure resources.

Deploy an ARM template that defines a Spot VM with eviction policy and max price settings.

Check the VM status to confirm it is running and ready to use.

Practice

1. What is the main benefit of using Azure Spot VMs?

easy

A. They automatically scale without any configuration.

B. They offer significant cost savings by using unused capacity.

C. They provide unlimited storage for virtual machines.

D. They guarantee 100% uptime for critical applications.

Solution

1. Step 1: Understand Azure Spot VM purpose

   Azure Spot VMs use spare capacity in Azure data centers, which is cheaper but can be interrupted.

2. Step 2: Identify the main benefit

   The main benefit is cost savings by using this spare capacity, not guaranteed uptime or unlimited storage.

3. Final Answer:

   They offer significant cost savings by using unused capacity. -> Option B

4. Quick Check:

   Spot VMs = Cost savings [OK]

Hint: Spot VMs save money by using spare capacity [OK]

Common Mistakes:

• Thinking Spot VMs guarantee uptime
• Confusing Spot VMs with premium storage
• Assuming Spot VMs auto-scale without setup

2. Which Azure CLI command option is used to create a Spot VM?

easy

A. --priority Spot

B. --spot-enabled true

C. --priority Standard

D. --vm-type Spot

Solution

1. Step 1: Recall Azure CLI syntax for Spot VMs

   To create a Spot VM, the correct option is --priority Spot.

2. Step 2: Eliminate incorrect options

   --priority Standard is for regular VMs; --spot-enabled and --vm-type are not valid Azure CLI options.

3. Final Answer:

   --priority Spot -> Option A

4. Quick Check:

   Spot VM creation uses --priority Spot [OK]

Hint: Use --priority Spot to create Spot VMs [OK]

Common Mistakes:

• Using --priority Standard instead of Spot
• Assuming --spot-enabled is valid
• Confusing VM type options

3. What happens if the max price you set for an Azure Spot VM is lower than the current Spot price?

medium

A. The VM will run but be charged the max price you set.

B. The VM will be created but with reduced performance.

C. The VM creation will fail due to price limit.

D. The VM will be created as a standard VM instead.

Solution

1. Step 1: Understand max price behavior

   The max price sets the highest price you agree to pay for the Spot VM.

2. Step 2: Analyze what happens if max price is too low

   If the current Spot price is higher than your max price, Azure will not create the VM to avoid exceeding your limit.

3. Final Answer:

   The VM creation will fail due to price limit. -> Option C

4. Quick Check:

   Max price below Spot price = VM creation fails [OK]

Hint: Spot VM fails if max price is below current Spot price [OK]

Common Mistakes:

• Thinking VM runs at max price anyway
• Assuming VM downgrades performance
• Believing VM converts to standard automatically

4. You created a Spot VM but it was unexpectedly evicted. What is the most likely cause?

medium

A. The VM was manually deleted by another user.

B. The VM ran out of disk space.

C. The VM exceeded the max price you set.

D. Azure needed the capacity back for other workloads.

Solution

1. Step 1: Understand Spot VM eviction reasons

   Spot VMs can be evicted when Azure reclaims capacity for higher priority workloads.

2. Step 2: Identify the most common eviction cause

   The most common cause is Azure needing the capacity back, not disk space or manual deletion.

3. Final Answer:

   Azure needed the capacity back for other workloads. -> Option D

4. Quick Check:

   Spot VM eviction = Azure reclaims capacity [OK]

Hint: Spot VMs evict when Azure reclaims capacity [OK]

Common Mistakes:

• Assuming eviction is due to disk space
• Thinking eviction happens if max price exceeded
• Believing eviction is always manual

5. You want to run a batch job that can be interrupted but must save costs. Which setup best uses Azure Spot VMs?

hard

A. Create Spot VMs with a max price set to your budget and use automatic eviction handling.

B. Create standard VMs with premium SSDs for guaranteed uptime.

C. Create Spot VMs without setting max price to avoid failures.

D. Use Azure Functions instead of VMs for batch jobs.

Solution

1. Step 1: Match workload needs to Spot VM features

   Batch jobs that can be interrupted fit Spot VMs well because they save costs but may be evicted.

2. Step 2: Choose best configuration for cost and reliability

   Setting a max price controls cost, and handling eviction automatically ensures job completion despite interruptions.

3. Step 3: Eliminate other options

   Standard VMs cost more; no max price risks failures; Azure Functions are different service types.

4. Final Answer:

   Create Spot VMs with a max price set to your budget and use automatic eviction handling. -> Option A

5. Quick Check:

   Spot VMs + max price + eviction handling = cost-effective batch jobs [OK]

Hint: Set max price and handle eviction for cost-effective Spot VMs [OK]

Common Mistakes:

• Not setting max price and risking high costs
• Choosing standard VMs for interruptible jobs
• Confusing Azure Functions with Spot VMs