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

Recall & Review

beginner

What is a Spot VM in Azure?

A Spot VM is a virtual machine that uses unused Azure capacity at a lower price. It can be evicted when Azure needs the capacity back.

beginner

Why are Spot VMs cheaper than regular VMs?

Spot VMs use spare capacity that Azure has available. Because this capacity can be taken back anytime, Azure offers Spot VMs at a lower price.

intermediate

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

Azure evicts the Spot VM, which means it stops or deletes the VM. You can choose to be notified before eviction or let it happen immediately.

intermediate

Which workloads are best suited for Spot VMs?

Workloads that can handle interruptions, like batch jobs, testing environments, or flexible applications, are best for Spot VMs.

intermediate

How can you protect important data on Spot VMs?

Store important data on separate persistent storage like Azure Disks or Azure Files, so data is safe even if the Spot VM is evicted.

What is the main reason Spot VMs are cheaper in Azure?

A They are only available in limited regions

B They have fewer features than regular VMs

C They run on slower hardware

D They use spare capacity that can be reclaimed

Spot VMs use spare capacity that Azure can reclaim, so they are offered at a lower price.

What happens when a Spot VM is evicted?

A It continues running without interruption

B Azure stops or deletes the VM

C The VM is upgraded automatically

D The VM is moved to another region

When Azure needs the capacity back, it stops or deletes the Spot VM, causing eviction.

Which workload is NOT ideal for Spot VMs?

A Critical production databases

B Testing environments

C Batch processing jobs

D Flexible web applications

Critical production databases require high availability and are not suited for Spot VMs due to possible eviction.

How can you prepare for Spot VM eviction?

A Ignore eviction notifications

B Use Spot VMs only for permanent workloads

C Store data on persistent storage outside the VM

D Disable eviction notifications

Storing data on persistent storage ensures data safety even if the Spot VM is evicted.

Which statement about Spot VMs is true?

A Spot VMs can be evicted anytime Azure needs capacity

B Spot VMs are always cheaper than reserved VMs

C Spot VMs cannot be used with Azure Scale Sets

D Spot VMs guarantee uninterrupted service

Spot VMs can be evicted anytime Azure reclaims capacity, so they do not guarantee uninterrupted service.

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

Think about how Azure sells unused resources cheaper but can take them back.

Describe strategies to handle data and workload interruptions when using Spot VMs.

Consider how to keep data safe and jobs running despite VM eviction.

Practice

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

easy

A. They automatically scale without any configuration.

B. They guarantee 100% uptime for critical applications.

C. They provide cheaper compute by using spare capacity.

D. They offer unlimited storage space for virtual machines.

Solution

1. Step 1: Understand Spot VM purpose

   Spot VMs use unused cloud capacity to offer lower prices.

2. Step 2: Compare benefits

   Unlike regular VMs, Spot VMs are cheaper but can be evicted when capacity is needed.

3. Final Answer:

   They provide cheaper compute by using spare capacity. -> Option C

4. Quick Check:

   Spot VMs = cheaper compute [OK]

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

Common Mistakes:

• Thinking Spot VMs guarantee uptime
• Confusing Spot VMs with auto-scaling
• Assuming Spot VMs provide extra storage

2. Which of the following is the correct way to set a Spot VM priority in Azure CLI?

easy

A. az vm create --priority High

B. az vm create --priority Spot

C. az vm create --spot-priority true

D. az vm create --enable-spot

Solution

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

   The correct parameter to set Spot VM priority is --priority Spot.

2. Step 2: Evaluate options

   The other options use incorrect or non-existent flags.

3. Final Answer:

   az vm create --priority Spot -> Option B

4. Quick Check:

   Spot VM priority flag = --priority Spot [OK]

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

Common Mistakes:

• Using incorrect flags like --spot-priority
• Setting priority to High instead of Spot
• Assuming --enable-spot is valid

3. Consider this Azure CLI command to create a Spot VM:

az vm create --name mySpotVM --image UbuntuLTS --priority Spot --max-price 0.05

What happens if the current Spot price exceeds 0.05 USD/hour?

medium

A. The VM is converted to a regular VM automatically.

B. The VM continues running at the higher price.

C. The VM price is capped at 0.05 USD/hour but runs normally.

D. The VM is evicted (stopped) automatically.

Solution

1. Step 1: Understand max-price setting

   The max-price limits the Spot VM cost; if price rises above it, eviction occurs.

2. Step 2: Analyze behavior when price exceeds max-price

   Spot VMs are stopped or deallocated automatically when price exceeds max-price.

3. Final Answer:

   The VM is evicted (stopped) automatically. -> Option D

4. Quick Check:

   Price > max-price = VM eviction [OK]

Hint: Spot VM stops if price goes above max-price [OK]

Common Mistakes:

• Thinking VM keeps running at higher price
• Assuming price is capped automatically
• Believing VM converts to regular VM

4. You tried to create a Spot VM with this command:

az vm create --name testVM --image UbuntuLTS --priority Spot --max-price -2

What is the issue with this command?

medium

A. max-price cannot be negative; it causes an error.

B. Priority Spot is invalid syntax.

C. Image UbuntuLTS is not supported for Spot VMs.

D. VM name testVM is reserved and cannot be used.

Solution

1. Step 1: Check max-price parameter rules

   max-price must be greater than or equal to -1; other negative values are invalid.

2. Step 2: Identify error cause

   Using -2 for max-price causes a validation error during VM creation.

3. Final Answer:

   max-price cannot be negative; it causes an error. -> Option A

4. Quick Check:

   max-price < -1 = error [OK]

Hint: max-price must be >= -1 [OK]

Common Mistakes:

• Using negative max-price values
• Thinking Spot priority syntax is wrong
• Assuming UbuntuLTS is unsupported

5. You want to run a batch job that can pause and resume without losing progress. Which Spot VM configuration helps minimize cost while ensuring the job restarts automatically if evicted?

hard

A. Set VM priority to Spot, max-price to a low value, and enable automatic redeployment.

B. Use regular VMs with high priority and no max-price limit.

C. Set VM priority to Spot with max-price set to -1 to avoid eviction.

D. Use Spot VMs without max-price and disable automatic redeployment.

Solution

1. Step 1: Choose Spot VM with cost control

   Setting priority to Spot and max-price low saves cost but risks eviction.

2. Step 2: Enable automatic redeployment

   Automatic redeployment restarts the VM if evicted, ensuring job resumes.

3. Final Answer:

   Set VM priority to Spot, max-price to a low value, and enable automatic redeployment. -> Option A

4. Quick Check:

   Spot + max-price + auto redeploy = cost saving + restart [OK]

Hint: Spot + low max-price + auto redeploy = cost + restart [OK]

Common Mistakes:

• Using negative max-price to avoid eviction
• Disabling automatic redeployment
• Choosing regular VMs for cost savings