Why VMs provide compute flexibility in Azure - Why It Works

Introduction

Virtual Machines (VMs) let you run many different software programs on one physical computer. They give you the power to change how much computing power you use, so you only pay for what you need.

When you want to run multiple different applications on one physical server without them interfering with each other

When you need to quickly add more computing power to handle more users or data

When you want to test new software safely without affecting your main system

When you want to move your applications easily between different physical servers

When you want to save money by using only the computing resources you need at any time

Commands

This command creates a new virtual machine in Azure with a small size to start. It sets up a user and SSH keys for secure access.

Terminal

az vm create --resource-group example-group --name example-vm --image UbuntuLTS --size Standard_B1s --admin-username azureuser --generate-ssh-keys

Expected Output

{

  "fqdns": "",

  "id": "/subscriptions/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/resourceGroups/example-group/providers/Microsoft.Compute/virtualMachines/example-vm",

  "location": "eastus",

  "name": "example-vm",

  "powerState": "VM running",

  "resourceGroup": "example-group",

  "zones": ""

}

→

--size - Sets the VM size which controls compute power

→

--image - Chooses the operating system for the VM

→

--generate-ssh-keys - Creates SSH keys for secure login

This command changes the VM to a bigger size with more CPU and memory to handle more work.

Terminal

az vm resize --resource-group example-group --name example-vm --size Standard_B2s

Expected Output

Succeeded

→

--size - Specifies the new VM size to increase compute resources

This command checks the current size of the VM to confirm the resize worked.

Terminal

az vm show --resource-group example-group --name example-vm --query "hardwareProfile.vmSize" -o tsv

Expected Output

Standard_B2s

Key Concept

If you remember nothing else from this pattern, remember: VMs let you quickly change computing power by resizing, giving you flexible control over resources.

Common Mistakes

Trying to resize a VM while it is running without stopping it first

Some VM sizes require the VM to be stopped before resizing, so the command will fail or cause errors

Stop the VM using 'az vm deallocate' before resizing, then start it again after resizing

Choosing a VM size that does not exist in the selected region

Azure does not offer all VM sizes in every region, so the creation or resize will fail

Check available VM sizes in the region with 'az vm list-sizes --location eastus' before creating or resizing

Summary

Create a VM with a chosen size to start with the right amount of compute power.

Resize the VM to increase or decrease compute resources as your needs change.

Verify the VM size after resizing to ensure the change was successful.

Practice

1. Why do virtual machines (VMs) provide flexibility in computing resources?

easy

A. Because they only run one fixed operating system

B. Because they require physical hardware upgrades for changes

C. Because they cannot be stopped once started

D. Because you can easily change their CPU, memory, and storage sizes

Solution

1. Step 1: Understand VM resource allocation

   VMs allow you to assign CPU, memory, and storage resources flexibly without changing physical hardware.

2. Step 2: Compare with fixed hardware

   Unlike physical machines, VMs can be resized or reconfigured quickly to meet changing needs.

3. Final Answer:

   Because you can easily change their CPU, memory, and storage sizes -> Option D

4. Quick Check:

   VM resource flexibility = changing CPU, memory, storage [OK]

Hint: VMs let you resize resources without hardware changes [OK]

Common Mistakes:

• Thinking VMs run only one OS
• Believing VMs can't be stopped or changed
• Confusing physical hardware upgrades with VM changes

2. Which of the following is the correct way to specify a VM size in Azure CLI?

easy

A. az vm create --type Standard_DS1_v2

B. az vm create --size Standard_DS1_v2

C. az vm create --memory 4GB

D. az vm create --cpu 2

Solution

1. Step 1: Identify correct VM size parameter

   Azure CLI uses the --size parameter to specify VM size like Standard_DS1_v2.

2. Step 2: Check other options

   --type, --memory, and --cpu are not valid parameters for VM size in this command.

3. Final Answer:

   az vm create --size Standard_DS1_v2 -> Option B

4. Quick Check:

   VM size uses --size parameter [OK]

Hint: Use --size to set VM size in Azure CLI commands [OK]

Common Mistakes:

• Using --type instead of --size
• Trying to set memory or CPU separately in create command
• Confusing VM size with VM type

3. Given this Azure VM scale set configuration snippet, what happens when demand increases?

{
  "sku": { "capacity": 2, "name": "Standard_DS1_v2" },
  "upgradePolicy": { "mode": "Manual" }
}

medium

A. The VM scale set stays at 2 VMs until manually changed

B. The VM scale set automatically adds more VMs to handle demand

C. The VM scale set deletes VMs when demand increases

D. The VM scale set changes VM size automatically

Solution

1. Step 1: Analyze the capacity and upgrade policy

   The capacity is set to 2, and upgrade mode is Manual, meaning no automatic scaling.

2. Step 2: Understand scaling behavior

   Since no autoscale is configured, the VM count stays fixed at 2 until manually changed.

3. Final Answer:

   The VM scale set stays at 2 VMs until manually changed -> Option A

4. Quick Check:

   Manual upgrade means no auto scaling [OK]

Hint: Manual mode means no automatic VM count changes [OK]

Common Mistakes:

• Assuming automatic scaling with Manual mode
• Thinking VM size changes automatically
• Confusing scale set with single VM behavior

4. You tried to resize an Azure VM but got an error. Which of these is the most likely cause?

medium

A. The VM size you chose does not exist in your region

B. You forgot to specify the VM name in the command

C. The VM is running and needs to be stopped before resizing

D. The VM is already the smallest size possible

Solution

1. Step 1: Check VM resize requirements

   VMs can be resized only to sizes available in the region where they run.

2. Step 2: Identify common resize errors

   If the chosen size is unavailable in the region, Azure returns an error.

3. Final Answer:

   The VM size you chose does not exist in your region -> Option A

4. Quick Check:

   Resize errors often due to unavailable sizes in region [OK]

Hint: Check VM size availability in your region before resizing [OK]

Common Mistakes:

• Assuming VM must be stopped for all resize types
• Ignoring region availability of VM sizes
• Forgetting to specify VM name causes different errors

5. You want to optimize costs by automatically adjusting VM resources based on workload. Which Azure feature should you use to achieve compute flexibility?

hard

A. Azure Active Directory for VM access control

B. Azure Blob Storage for VM backups

C. Azure VM Scale Sets with autoscaling rules

D. Azure Virtual Network peering

Solution

1. Step 1: Identify cost optimization via resource adjustment

   Automatically adjusting VM count or size based on workload is done by autoscaling.

2. Step 2: Match feature to autoscaling

   Azure VM Scale Sets support autoscaling rules to add or remove VMs dynamically.

3. Step 3: Exclude unrelated features

   Blob Storage, Virtual Network peering, and Active Directory do not manage VM compute scaling.

4. Final Answer:

   Azure VM Scale Sets with autoscaling rules -> Option C

5. Quick Check:

   Autoscaling VM Scale Sets = compute flexibility and cost saving [OK]

Hint: Use VM Scale Sets autoscaling to adjust resources automatically [OK]

Common Mistakes:

• Confusing storage or network features with compute scaling
• Thinking access control manages resource scaling
• Ignoring autoscaling capabilities of VM Scale Sets