Proposed Pull Request Change

📄 Document Links

View on GitHub View on Microsoft Learn

--- title: Migrate low-priority VMs to spot VMs in Batch description: Learn how to migrate Azure Batch low-priority VMs to Spot VMs and plan for feature end of support. author: padmalathas ms.author: padmalathas ms.service: azure-batch ms.topic: how-to ms.date: 11/20/2025 # Customer intent: As an Azure Batch user, I want to migrate my low-priority VMs to Spot VMs before the retirement deadline, so that I can continue to benefit from cost-effective compute resources without service disruption. --- # Migrate Batch low-priority VMs to Spot VMs The ability to allocate low-priority compute nodes in Azure Batch pools is being retired on *September 30, 2025*. Learn how to migrate your Batch pools with low-priority compute nodes to compute nodes based on Spot instances. ## About the feature Currently, as part of a Batch pool configuration, you can specify a target number of low-priority compute nodes for Batch managed pool allocation Batch accounts. In user subscription pool allocation Batch accounts, you can specify a target number of spot compute nodes. In both cases, these compute resources are allocated from spare capacity and offered at a discount compared to dedicated, on-demand VMs. The amount of unused capacity that's available varies depending on factors such as VM family, VM size, region, and time of day. Unlike dedicated capacity, these low-priority or spot VMs can be reclaimed at any time by Azure. Therefore, low-priority and spot VMs are typically viable for Batch workloads that are amenable to interruption or don't require strict completion timeframes to potentially lower costs. ## Feature end of support Only low-priority compute nodes in Batch are being retired. Spot compute nodes will continue to be supported, is a GA offering, and not affected by this deprecation. On September 30, 2025, we'll retire low-priority compute nodes. After that date, existing low-priority pools in Batch may no longer be usable, attempts to seek back to target low-priority node counts will fail, and you'll no longer be able to provision new pools with low-priority compute nodes. ## Alternative: Use Azure Spot-based compute nodes in Batch pools As of December 2021, Azure Batch began offering Spot-based compute nodes in Batch. Like low-priority VMs, you can use spot instances to obtain spare capacity at a discounted price in exchange for the possibility that the VM will be preempted. If a preemption occurs, the spot compute node will be evicted and all work that wasn't appropriately checkpointed will be lost. Checkpointing is optional and is up to the Batch end-user to implement. The running Batch task that was interrupted due to preemption will be automatically requeued for execution by a different compute node. Additionally, Azure Batch will automatically attempt to seek back to the target Spot node count as specified on the pool. ### What changes during migration When migrating from low-priority to Spot VMs, the following pool configuration properties are affected: - **Pool allocation mode**: Must be `UserSubscription` (Spot VMs are not available in `BatchService` mode) - **VM configuration**: Must be `VirtualMachineConfiguration` (not supported in `CloudServiceConfiguration`) - **Target node properties**: - `targetLowPriorityNodes` → `targetSpotNodes` - Pool pricing model changes from low-priority to Spot pricing - Eviction policy becomes configurable (delete or deallocate) See the [detailed breakdown](batch-spot-vms.md) between the low-priority and spot offering in Batch. ## Migrate a Batch pool with low-priority compute nodes or create a Batch pool with Spot instances ### Prerequisites 1. Ensure that you're using a [user subscription pool allocation mode Batch account](batch-account-create-portal.md). 1. Verify your pool uses `VirtualMachineConfiguration` (Spot VMs are not supported in `CloudServiceConfiguration`). ### Option 1: Azure CLI Migration (Recommended for automation) #### Create a new pool with Spot instances: ```azurecli-interactive az batch pool create \ --id "spot-pool-001" \ --vm-size "Standard_D2s_v3" \ --target-low-priority-nodes 5 \ --enable-inter-node-communication false \ --image "Canonical:0001-com-ubuntu-server-focal:20_04-lts-gen2" \ --node-agent-sku-id "batch.node.ubuntu 20.04" \ --account-name <your-batch-account-name> \ --account-endpoint "https://<your-batch-account-name>.<region>.batch.azure.com" ``` #### Scale existing pool to use Spot instances: ```azurecli-interactive az batch pool resize \ --pool-id <existing-pool-id> \ --target-dedicated-nodes 0 \ --target-low-priority-nodes 5 \ --account-name <your-batch-account-name> \ --account-endpoint "https://<your-batch-account-name>.<region>.batch.azure.com" ``` ### Option 2: Azure PowerShell (Alternative automation method) #### Create pool with Spot instances: ```powershell New-AzBatchPool ` -Id "spot-pool-001" ` -VirtualMachineSize "Standard_D2s_v3" ` -TargetLowPriorityComputeNodes 5 ` -VirtualMachineImageId "/subscriptions/{subscription}/resourceGroups/{rg}/providers/Microsoft.Compute/images/{image}" ` -BatchContext $context ``` #### Validate with PowerShell: ```powershell $pool = Get-AzBatchPool -Id "spot-pool-001" -BatchContext $context $pool | Select-Object Id, VmSize, @{Name="SpotNodes";Expression={$_.TargetLowPriorityComputeNodes}}, State ``` ### Option 3: Azure portal (UI method) 1. In the Azure portal, select the Batch account and view an existing pool or create a new pool. 1. Under **Scale**, select either **Target dedicated nodes** or **Target Spot/low-priority nodes**. :::image type="content" source="media/certificates/low-priority-vms-scale-target-nodes.png" alt-text="Screenshot that shows how to scale target nodes."::: 1. For an existing pool, select the pool, and then select **Scale** to update the number of spot nodes required based on the job scheduled. 1. Select **Save**. ## Validate the Migration ### Check pool configuration after migration: ```azurecli-interactive az batch pool show \ --account-name <your-batch-account-name> \ --account-endpoint "https://<your-batch-account-name>.<region>.batch.azure.com" \ --pool-id <your-pool-id> \ --query "{PoolID:id, VMSize:vmSize, SpotNodes:scaleSettings.targetLowPriorityNodes, AllocationMode:poolAllocationMode, VMConfig:virtualMachineConfiguration.nodeAgentSkuId}" ``` ### Expected successful output: ```json { "AllocationMode": "UserSubscription", "PoolID": "spot-pool-001", "SpotNodes": 5, "VMConfig": "batch.node.ubuntu 20.04", "VMSize": "Standard_D2s_v3" } ``` ### Check pool state and node allocation: ```azurecli-interactive az batch pool show \ --account-name <your-batch-account-name> \ --account-endpoint "https://<your-batch-account-name>.<region>.batch.azure.com" \ --pool-id <your-pool-id> \ --query "{State:state, CurrentSpotNodes:currentLowPriorityNodes, TargetSpotNodes:scaleSettings.targetLowPriorityNodes, ResizeErrors:resizeErrors}" ``` ### Expected output for healthy pool: ```json { "CurrentSpotNodes": 5, "ResizeErrors": null, "State": "steady", "TargetSpotNodes": 5 } ``` ### Troubleshooting: What indicates a problem? - **State**: `"resizing"` (for extended periods) indicates allocation issues - **ResizeErrors**: Any non-null value indicates capacity or quota issues - **CurrentSpotNodes** < **TargetSpotNodes**: Pool hasn't reached target capacity ## Configuration Variables for Automation For teams building automated solutions, these are the key configuration properties and their values: ### REST API Properties - **Pool allocation mode**: `poolAllocationMode: "UserSubscription"` - **VM configuration type**: `virtualMachineConfiguration` (required) - **Target Spot nodes**: `targetLowPriorityNodes: <number>` - **Eviction policy**: `virtualMachineConfiguration.spotPolicy.evictionPolicy: "delete"` or `"deallocate"` ### ARM Template Variables ```json { "poolAllocationMode": "UserSubscription", "scaleSettings": { "targetDedicatedNodes": 0, "targetLowPriorityNodes": 5 }, "virtualMachineConfiguration": { "imageReference": {...}, "nodeAgentSkuId": "batch.node.ubuntu 20.04" } } ``` ### Terraform Configuration ```hcl resource "azurerm_batch_pool" "spot_pool" { pool_allocation_mode = "UserSubscription" scale_settings { target_dedicated_nodes = 0 target_low_priority_nodes = 5 } virtual_machine_configuration { image_reference {...} node_agent_sku_id = "batch.node.ubuntu 20.04" } } ``` ## FAQs - How do I create a user subscription pool allocation Batch account? See the [quickstart](./batch-account-create-portal.md) to create a new Batch account in user subscription pool allocation mode. - Are Spot VMs available in Batch managed pool allocation accounts? No. Spot VMs are available only in user subscription pool allocation Batch accounts. - Are spot instances available for `CloudServiceConfiguration` Pools? No. Spot instances are only available for `VirtualMachineConfiguration` pools. `CloudServiceConfiguration` pools will be [retired](https://azure.microsoft.com/updates/azure-batch-cloudserviceconfiguration-pools-will-be-retired-on-29-february-2024/) before low-priority pools. We recommend that you migrate to `VirtualMachineConfiguration` pools and user subscription pool allocation Batch accounts before then. - What is the pricing and eviction policy of spot instances? Can I view pricing history and eviction rates? Yes. In the Azure portal, you can see historical pricing and eviction rates per size in a region. For more information about using spot VMs, see [Spot Virtual Machines](/azure/virtual-machines/spot-vms). - Can I transfer my quotas between Batch accounts? Currently you can't transfer any quotas between Batch accounts. ## Next steps See the [Batch Spot compute instance guide](batch-spot-vms.md) for details on further details in the difference between offerings, limitations, and deployment examples.