Getting Started With Virtual Machine Scale Set: A practical Guide

Source: Dev.to

What is a Virtual Machine Scale Set (VMSS)?

A Virtual Machine Scale Set is a resource that lets you deploy and manage a set of identical virtual machines.

• Create many VMs with the same configuration.
• Scale up/down (vertical) or out/in (horizontal) based on demand.
• Built‑in features: load balancing, high availability, and auto‑scaling.

Ways to Create a Virtual Machine Scale Set

There are two ways to create a VMSS in the Azure portal:

1. Search‑and‑Create – Type Virtual Machine Scale Set in the portal search bar, select it, and follow the wizard.
2. Replicate an Existing VM – Create a VMSS by using an existing virtual machine as a source image.

In this guide we’ll walk through the replication method.

Step 1 – Create an Azure Compute Gallery

The compute gallery and the source VM must reside in the same resource group.

1. Search for “Azure compute gallery” in the Azure portal and select Azure Compute Galleries.

   

2. Click the + Create button.

   

3. Choose the resource group that contains the VM you want to replicate.

   

4. Give the gallery a name – for this tutorial we’ll use holigallery.

   

5. Click Review + create.

   

6. When validation passes, click Create.

   

7. After deployment completes, click Go to resource.

   

Step 2 – Capture the Source VM as an Image

1. Return to the Azure portal home (click Microsoft Azure at the top‑left) and open the virtual machine you want to replicate.

   

2. In the VM’s blade, click Capture.

   

3. In the Create image pane, fill in:

   • Image name – e.g., myVmImage.
   • Resource group – same as the compute gallery’s group.
   • Image type – select Image (not snapshot).
   • Gallery – choose the gallery you created (holigallery).
   • Version – accept the default or specify a version number.

4. Click Review + create, then Create. Azure will generate an image and store it in the compute gallery.

Step 3 – Build the VM Scale Set from the Image

1. In the portal search bar, type Virtual Machine Scale Set and select it.
2. Click + Create and fill out the basics (subscription, resource group, VMSS name, region).
3. Under Image, choose My Items → Gallery → holigallery → myVmImage.
4. Configure the instance size, instance count, networking, and scaling policy as required.
5. Review the settings and click Create. Azure will provision a scale set based on the captured image.

Summary

• VMSS lets you manage identical VMs with built‑in scaling, load balancing, and high availability.

• You can create a VMSS by search‑and‑create or by replicating an existing VM.

• The replication workflow involves:

  1. Creating an Azure Compute Gallery.
  2. Capturing the source VM as an image stored in that gallery.
  3. Building a Virtual Machine Scale Set from the gallery image.

Follow these steps to quickly spin up a scalable set of VMs that share the exact configuration of your existing machine. Happy scaling!

Step‑by‑Step Guide

1. Add the image

   ![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/dly74rvq355613beszu2.png)

2. Select the gallery – Click the dropdown sign and choose the gallery where you want to put the image.

   

3. Operating System state – Choose Specialized.

   • Specialized – No password or username is required before the VM can be used.
   • Generalized – A password and username are required.

   

4. Name the VM – Click Create new, type a name for the new VM, then click OK.

   

5. Version details – Enter a version number (e.g., 0.0.1, 0.0.2, 15.35.0).

   

6. Review + create – Click the Review + create button.

   

7. Validate and create – Wait until Validation passed appears, then click Create.

   

8. Go to resource – After deployment finishes, click Go to resource.

   

9. Create a VM Scale Set (VMSS) – Click + Create VMSS.

   

10. Scale set details – Provide a name for the Virtual Machine Scale Set.

    

11. Select orchestration mode – Choose between Flexible and Uniform.

    • Flexible – Highly available with multiple identical VMs.
    • Uniform – Suited for large‑scale, stateless workloads.

    For this guide we select Flexible.

    

12. Review + create – Click Review + create again.

    

13. Validate and create – Wait for Validation passed, then click Create.

    

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22. Wait for your deployment to complete and click **Go to resource**

[![Deployment complete screenshot](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9gq4f5xb5h4huvreee94.png)](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9gq4f5xb5h4huvreee94.png)

23. Congratulations! Your **Virtual Machine Scale Set** is ready

[![VM Scale Set ready screenshot](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ousv1jquu4kl5mm0bkwr.png)](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ousv1jquu4kl5mm0bkwr.png)