Azure Spot VMs for cost savings - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are Azure Spot VMs?

Azure Spot VMs are virtual machines offered at a lower price because they use unused Azure capacity. They can be evicted when Azure needs the capacity back.

beginner

Why are Azure Spot VMs cheaper than regular VMs?

They use spare capacity in Azure datacenters, so Microsoft offers them at a discount. However, they can be stopped or evicted anytime when capacity is needed for other customers.

intermediate

What happens when Azure needs the capacity used by a Spot VM?

The Spot VM is evicted, which means it is stopped or deleted depending on the eviction policy. You lose the VM and any data on temporary storage unless saved elsewhere.

intermediate

Which workloads are best suited for Azure Spot VMs?

Workloads that can handle interruptions, like batch jobs, testing environments, or flexible applications that can restart without data loss.

beginner

How can you protect important data when using Azure Spot VMs?

By saving data on durable storage like Azure Disks or Azure Blob Storage, not on the VM's temporary storage which is lost on eviction.

What is the main reason Azure Spot VMs are cheaper than regular VMs?

A They run on slower hardware

B They have fewer features

C They use spare Azure capacity that can be reclaimed

D They have limited network access

Azure Spot VMs use unused capacity in Azure datacenters, so they are offered at a discount but can be evicted when needed.

What happens to a Spot VM when Azure needs the capacity back?

A It continues running without interruption

B It is evicted (stopped or deleted)

C It automatically upgrades to a regular VM

D It is paused indefinitely

Spot VMs can be evicted by Azure when capacity is needed, meaning they are stopped or deleted based on eviction policy.

Which type of workload is NOT ideal for Azure Spot VMs?

A Critical production databases

B Testing environments

C Batch processing jobs

D Flexible applications that can restart

Critical production databases require high availability and cannot tolerate interruptions, so Spot VMs are not suitable.

How should you store important data when using Azure Spot VMs?

A On durable Azure storage like disks or blobs

B Only on the VM's temporary storage

C On local machine outside Azure

D No need to store data separately

Data should be saved on durable Azure storage because temporary storage on Spot VMs is lost on eviction.

What is a key benefit of using Azure Spot VMs?

A Free technical support

B Guaranteed uptime

C Unlimited storage capacity

D Significant cost savings for interruptible workloads

Azure Spot VMs offer lower prices but can be evicted, making them ideal for workloads that can handle interruptions and save costs.

Explain what Azure Spot VMs are and how they help save costs.

Think about spare capacity and interruptions.

Describe best practices for using Azure Spot VMs safely.

Focus on data safety and workload type.

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