Correct way of creating a Azure VM Scale Set?

[btastic]

Hello there,

we are currently struggling with performance issues with our (VMSS) self-hosted agents. Some time ago, we took the scripts from this repository and modified it to create our own azure image with customizations, which is basically removing most of the capabilities we don't need. For example, java, web related stuff, android etc. Just to have quicker builds and smaller images.

However, we recently noticed that dotnet restore and dotnet build tasks take a long time on more complex solutions.

Today I build a fresh new image from this repository, but it does not come close to the performance of the Azure Hosted agents.

When a Azure Hosted Agent on Ubuntu 24.04 builds one of our more complex solutions, it takes around 30 seconds to restore and 1m15s to build. But apparently when I host the same image in an azure scale set, restoring takes around 2m30s and building takes around 8 minutes.

I have no idea where else to look. The image generation is completely automated by (I suppose) the same standards as the Hosted Agents in Azure. So, for me there is only one place to look, and that is the scale set that uses the created Image.

Currently I have created the image as per this guide: https://learn.microsoft.com/en-us/azure/devops/pipelines/agents/scale-set-agents?view=azure-devops

How would I go about analyzing the performance issues?

I am completely clueless, and I spent way too much time on this, so I need some advice on what to do.