Now in Preview – Spot priority mix for Azure Virtual Machine Scale Sets

Today we are announcing the preview of Spot priority mix for Azure Virtual Machine Scale Sets (VMSS) with flexible orchestration. This new capability allows you to create and expand a VM (virtual machine) scale set containing both Spot VMs and standard VMs. You will now have the flexibility to run a mix of standard and Spot VMs for VMSS deployments, and easily achieve a balance between availability and lower infrastructure costs based on your workload requirements.  

With this new capability, you can now specify the minimum number of standard VMs you would like to run in a scale set in addition to specifying the % split between Spot and standard VMs that must be maintained when scaling above the minimum standard VM count. If Spot VM capacity becomes unavailable, then you can specify whether the scale-out operation should create standard VMs not to impact overall availability and performance during periods of high demand.  

The ability to mix Spot and standard VMs gives you additional VMSS management capabilities to:  

• Reduce compute infrastructure costs by leveraging the deep discounts that Spot VMs can provide while maintaining the compute capacity your workload needs.  
• Simplify the scale out and scale in operations of compute workloads that require both Spot and standard VMs by letting Azure orchestrate the creation or deletion of the appropriate mix of VM types. 

Spot priority mix can be useful in a variety of scenarios. Here’s a couple of examples:  

1. Run time bound financial risk management and modeling workloads without compromising on the baseline performance but delivering faster results and cost savings by adding Spot VMs.  
2. Run web-services and load-balancing workloads for an e-commerce site at scale by mixing Spot and standard VMs of the same VM type and size to maximize your workload efficiency and resiliency.  

How to set up Spot priority mix using ARM REST API   

To create a VM Scale Set with a mix of standard and Spot VMs, simply add the following properties to the scale set with flexible orchestration mode using a virtual machine profile: 

New Parameters: 

• baseRegularPriorityCount – specifies a base number of standard VMs; if the scale set capacity is at or below this number, all VMs will be standard VMs.  
• regularPriorityPercentageAboveBase – specifies the percentage split of standard and Spot VMs that will be used when the scale set capacity is above the baseRegularPriorityCount.  

Try out Spot priority mix: 

The Azure portal helps you to locate Virtual Machine Scale Set as one of the Azure services. You can then select the orchestration mode as “flexible” and choose the “Run with Azure Spot discount” option: 

Configure your Spot VM using “Azure Spot configuration” by setting the eviction type, policy, and selecting the VM size. 

Move on to “Scaling” tab to specify your initial instance count, select “Scale with VMs and discounted Spot VMs” and proceed to specify your base VM and percentage distribution of standard (on-demand) and Spot VMs  

Available now: 

Spot priority Mix is available now in preview with Azure Virtual Machine Scale Sets flexible orchestration mode in all Azure regions except China.

Learn more by reading the documentation.