Azure devops Agent Pools vs Parallel jobs

Question

I am using my own Azure VM scale set as the agent pool in Azure devops. The VM scale set consists of 3 nodes. However whenever running multiple jobs at the same time, only one agent is scheduling the jobs and the others are idle.

It seems that I need to purchase parallel jobs separately for running jobs in parallel. Does anyone know the difference between using your own VM scale set for the agent pools and running parallel jobs using parallel jobs?

Even though VM scale sets are used (which are less costly) do we need to still purchases parallel jobs ($40 per agent) ?

Answer 1

You need to still purchases parallel jobs.

You can just consider VM scale set agents as one of your private agent pools, which Azure Pipelines can automatically scale-up or scale-down the number of agents based on number of incoming pipeline jobs. See document here for more information.

Azure virtual machine scale set agents, hereafter referred to as scale set agents, are a form of self-hosted agents that can be autoscaled to meet your demands

Below is the concept of Jobs:

A stage contains one or more jobs. Each job runs on an agent. A job represents an execution boundary of a set of steps. All of the steps run together on the same agent

So we can know that scale set agents and Parallel jobs are different things. parallel jobs will run on the scale set agents. And Azure Pipelines will automatically scale the number of agents according to the number of parallel jobs.

If your azure devops project is private. You only get One free job; So You still need to purchases parallel jobs. See here for more information.