Azure Spot VMs for cost savings - Step-by-Step Execution

Process Flow - Azure Spot VMs for cost savings

Request Spot VM

↓

Check Available Capacity

Yes↓

Allocate Spot VM at Discounted Price

↓

Run Workload

↓

If Capacity Lost or Price Exceeds Max

Yes↓

Evict Spot VM

↓

Option: Redeploy or Stop

Back to Request Spot VM↓

Wait or Use Regular VM

↩Back to Request Spot VM

The flow shows requesting a Spot VM, checking capacity and price, running workload, and handling eviction if capacity or price conditions change.

Execution Sample

Azure

Request Spot VM with max price $0.05
If capacity available and price <= max
  Allocate Spot VM
Run workload
If eviction signal received
  Evict VM

This code requests a Spot VM at a max price, runs workload if allocated, and evicts VM if Azure reclaims capacity.

Process Table

Step	Action	Capacity Available?	Current Spot Price	Max Price	VM Allocated?	Eviction Signal	Result
1	Request Spot VM	Yes	$0.04	$0.05	No	No	Check capacity and price
2	Evaluate price and capacity	Yes	$0.04	$0.05	Yes	No	Allocate Spot VM
3	Run workload	Yes	$0.04	$0.05	Yes	No	Workload running
4	Price rises to $0.06	Yes	$0.06	$0.05	Yes	No	Price exceeds max, eviction imminent
5	Eviction signal received	Yes	$0.06	$0.05	Yes	Yes	Evict Spot VM
6	Redeploy or stop	No	$0.06	$0.05	No	No	VM stopped or redeployed
7	Request Spot VM again	No	$0.06	$0.05	No	No	Capacity unavailable, wait or use regular VM

💡 Execution stops when capacity is unavailable or VM is evicted due to price or capacity changes.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7
Capacity Available	Unknown	Yes	Yes	Yes	Yes	Yes	No	No
Current Spot Price	Unknown	$0.04	$0.04	$0.04	$0.06	$0.06	$0.06	$0.06
Max Price	$0.05	$0.05	$0.05	$0.05	$0.05	$0.05	$0.05	$0.05
VM Allocated	No	No	Yes	Yes	Yes	Yes	No	No
Eviction Signal	No	No	No	No	No	Yes	No	No

Key Moments - 3 Insights

Why is the Spot VM evicted even though capacity is still available?

Because the current Spot price rose above the max price set by the user (see Step 4 and Step 5 in execution_table), Azure evicts the VM to reclaim capacity.

What happens if capacity is not available when requesting a Spot VM?

The VM is not allocated (Step 7 in execution_table). The user can wait or choose a regular VM instead.

Does the VM run continuously once allocated?

No, the VM runs until Azure sends an eviction signal due to price or capacity changes (Step 3 to Step 5).

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the Spot VM first allocated?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Check the 'VM Allocated?' column in execution_table rows.

According to variable_tracker, what is the 'Current Spot Price' after Step 4?

A $0.04

B $0.05

C $0.06

D Unknown

💡 Hint

Look at the 'Current Spot Price' row under 'After Step 4' in variable_tracker.

If the max price was increased to $0.07, what would happen at Step 4 in execution_table?

A VM would continue running as price is below max

B VM would be evicted due to price

C Capacity would become unavailable

D Eviction signal would be ignored

💡 Hint

Compare 'Current Spot Price' and 'Max Price' columns in execution_table at Step 4.

Concept Snapshot

Azure Spot VMs let you use spare capacity at a discount.
You set a max price you are willing to pay.
VMs run until Azure reclaims capacity or price rises above max.
Evicted VMs stop or can be redeployed.
Best for interruptible, flexible workloads.

Full Transcript

Azure Spot VMs provide cost savings by using spare capacity at discounted prices. You request a Spot VM with a maximum price you agree to pay. If capacity is available and the current Spot price is at or below your max price, Azure allocates the Spot VM. Your workload runs on this VM. However, if Azure needs the capacity back or if the Spot price rises above your max price, Azure sends an eviction signal and the VM is stopped or redeployed. If capacity is unavailable when requesting, the VM is not allocated and you can wait or use a regular VM. This approach is ideal for workloads that can handle interruptions and want to save costs.

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