Hello Wes Verhagen,
Welcome to the Microsoft Q&A forum.
It seems like you have configured the ADX cluster with "Optimized autoscale" https://video2.skills-academy.com/en-us/azure/data-explorer/manage-cluster-horizontal-scaling?WT.mc_id=Portal-Microsoft_Azure_Kusto#optimized-autoscale-recommended-option
Optimized autoscale:
Optimized Autoscale is a built-in feature that helps clusters perform their best when demand changes. You can choose to scale your cluster manually to a specific instance count, or via a custom Optimized Autoscale policy that scales based on metric(s) thresholds. Optimized Autoscale enables your cluster to be performant and cost effective by adding and removing instances based on demand
- If the cluster is underutilized, it is scaled in to lower cost without affecting the required performance.
- If the cluster is overutilized, it is scaled out to maintain optimal performance
In your case, the changes in VM types (from D1 v2 to D2 v2 and D3 v2) are likely due to the Optimized Autoscale feature responding to varying demands on your cluster.
To have more control over the scaling and potentially reduce costs, you might want to look into the custom autoscale feature. Custom autoscale allows you to set specific policies and thresholds for scaling based on your needs.
I hope this helps. Please let me know if you have any further questions.