Deploy a scale set using Instance Mix

The article walks through how to deploy a scale set using Instance Mix.

Important

Instance Mix for Virtual Machine Scale Sets with Flexible Orchestration Mode is currently in preview. Previews are made available to you on the condition that you agree to the supplemental terms of use. Some aspects of this feature may change prior to general availability (GA).

Prerequisites

Before using Instance Mix, complete feature registration for the FlexVMScaleSetSkuProfileEnabled feature flag using the az feature register command:

az feature register --namespace "Microsoft.Compute" --name "FlexVMScaleSetSkuProfileEnabled"

It takes a few moments for the feature to register. Verify the registration status by using the az feature show command:

az feature show --namespace "Microsoft.Compute" --name "FlexVMScaleSetSkuProfileEnabled"

Create a scale set using Instance Mix

Azure portal

1. Go to Virtual machine scale sets.
2. Select the Create button to go to the Create a virtual machine scale set view.
3. In the Basics tab, fill out the required fields. If the field isn't called out in the next sections, you can set the fields to what works best for your scale set.
4. Ensure that you select a region that Instance Mix is supported in.
5. Be sure Orchestration mode is set to Flexible.
6. In the Size section, click Select up to 5 sizes (preview) and the Select a VM size page appears.
7. Use the size picker to select up to five VM sizes. Once you've selected your VM sizes, click the Select button at the bottom of the page to return to the scale set Basics tab.
8. In the Allocation strategy (preview) field, select your allocation strategy.
9. When using the Prioritized allocation strategy, the Rank size section appears below the Allocation strategy section. Clicking on the bottom Rank priority brings up the prioritization blade, where you can adjust the priority of your VM sizes.
10. You can specify other properties in subsequent tabs, or you can go to Review + create and select the Create button at the bottom of the page to start your Instance Mix scale set deployment.

Azure CLI

You can use the following basic command to create a scale set using Instance Mix using the following command, which will default to using the lowestPrice allocation strategy:

az vmss create \
  --name {myVMSS} \
  --resource-group {myResourceGroup} \
  --image ubuntu2204 \
  --vm-sku Mix \
  --skuprofile-vmsizes Standard_DS1_v2 Standard_D2s_v4

To specify the allocation strategy, use the --skuprofile-allocation-strategy parameter, like the following:

az vmss create \
  --name {myVMSS} \
  --resource-group {myResourceGroup} \
  --image ubuntu2204 \
  --vm-sku Mix \
  --skuprofile-vmsizes Standard_DS1_v2 Standard_D2s_v4 \
  --skuprofile-allocation-strategy CapacityOptimized

Azure PowerShell

You can use the following basic command to create a scale set using Instance Mix using the following command, which will default to using the lowestPrice allocation strategy:

New-AzVmss `
  -ResourceGroupName $resourceGroupName `
  -Credential $credentials `
  -VMScaleSetName $vmssName `
  -DomainNameLabel $domainNameLabel1 `
  -VMSize "Mix" `
  -SkuProfileVmSize @("Standard_D4s_v3", "Standard_D4s_v4");

To specify the allocation strategy, use the SkuProfileAllocationStrategy parameter, like the following:

New-AzVmss `
-ResourceGroupName $resourceGroupName `
-Credential $credentials `
-VMScaleSetName $vmssName `
-DomainNameLabel $domainNameLabel1 `
-SkuProfileVmSize @("Standard_D4s_v3", "Standard_D4s_v4") `
-SkuProfileAllocationStrategy "CapacityOptimized";

To create a scale set using a scale set configuration object utilizing Instance Mix, use the following command:

$vmss = New-AzVmssConfig -Location $loc -SkuCapacity 2 -UpgradePolicyMode 'Manual' -EncryptionAtHost -SecurityType $stnd -SkuProfileVmSize @("Standard_D4s_v3", "Standard_D4s_v4") -SkuProfileAllocationStrategy "CapacityOptimized"`
            | Add-AzVmssNetworkInterfaceConfiguration -Name 'test' -Primary $true -IPConfiguration $ipCfg `
            | Set-AzVmssOSProfile -ComputerNamePrefix 'test' -AdminUsername $adminUsername -AdminPassword $adminPassword `
            | Set-AzVmssStorageProfile -OsDiskCreateOption 'FromImage' -OsDiskCaching 'None' `
            -ImageReferenceOffer $imgRef.Offer -ImageReferenceSku $imgRef.Skus -ImageReferenceVersion 'latest' `
            -ImageReferencePublisher $imgRef.PublisherName;
 
$vmssResult = New-AzVmss -ResourceGroupName $resourceGroupName -Name $vmssName -VirtualMachineScaleSet $vmss

REST API

To deploy an Instance Mix scale set through REST API, use a PUT call to and include the following sections in your request body:

PUT https://management.azure.com/subscriptions/{YourSubscriptionId}/resourceGroups/{YourResourceGroupName}/providers/Microsoft.Compute/virtualMachineScaleSets/{youScaleSetName}?api-version=2023-09-01

In the request body, ensure sku.name is set to Mix:

  "sku": {
    "name": "Mix",
    "capacity": {TotalNumberVMs}
  },

Ensure you reference your existing subnet:

"subnet": {
    "id": "/subscriptions/{YourSubscriptionId}/resourceGroups/{YourResourceGroupName}/providers/Microsoft.Network/virtualNetworks/{YourVnetName}/subnets/default"
},

Lastly, be sure to specify the skuProfile with up to five VM sizes. This sample uses three:

    "skuProfile": {
      "vmSizes": [
        {
          "name": "Standard_D8s_v5"
        },
        {
          "name": "Standard_E16s_v5"
        },
        {
          "name": "Standard_D2s_v5"
        }
      ],
      "allocationStrategy": "lowestPrice"
    },

When using the prioritized allocation strategy, you can specify the priority ranking of the vmSizes specified:

    "skuProfile": {
      "vmSizes": [
        {
          "name": "Standard_D8s_v5", "rank": 1
        },
        {
          "name": "Standard_E16s_v5", "rank": 2
        },
        {
          "name": "Standard_D2s_v5", "rank": 1
        }
      ],
      "allocationStrategy": "Prioritized"
    },

Next steps

Learn how to troubleshoot your Instance Mix enabled scale set.