Revise blog on AKS capacity management strategies

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+---
+title: "Navigating Capacity Challenges on AKS with Node Auto Provisioning or Virtual Machine Node Pools"
+description: "Learn how Node auto provisioning and Virtual Machine node pools can address capacity constraints when scaling an AKS cluster"
+date: 2025-11-26
+authors: ["wilson darko"]
+tags:
+  - node-auto-provisioning
+  - vm-node-pools
+---
+
+## When Growth Meets a Wall
+Imagine this: your application is thriving, traffic spikes, and Kubernetes promises elasticity. You hit “scale,” expecting magic—only to be greeted by cryptic errors like:
+
+- **Insufficient regional capacity**: Azure can’t allocate the VM size you requested in a particular region or zone.
+- **Quota exceeded**: Your subscription has hit its compute limits for a particular location or VM Size.
+- **Zonal allocation failure**: The VM Size (also referred to as VM SKU) you chose isn’t available in the zone.
+
+For customers, these aren’t just error messages - they’re roadblocks. Pods remain pending, deployments stall, and SLAs tremble. Scaling isn’t just about adding nodes; it’s about finding capacity in a dynamic, multi-tenant cloud where demand often outpaces supply. In the case of quota gaps, usually a user can increase their quota in a particular location - but what about when a specific virtual machine size (also known as "VM SKU") is simply unavailable? This can cause many challenges for users.
+
+---
+
+<!-- truncate -->
+
+:::info
+
+Learn more in the official documentation: [Node Auto Provisioning](https://learn.microsoft.com/azure/aks/node-auto-provisioning) or [Virtual Machine Node Pool](https://learn.microsoft.com/azure/aks/virtual-machines-node-pools)
+
+:::
+
+---
+
+## The Hidden Complexity Behind Capacity
+When using Kubernetes, every node pool is typically tied to a specific VM SKU, region, and zone, which can require some effort to update. In some scaling scenarios, high-demand VM SKUs can become unavailable in certain regions or zones. In this case node pools being limited to one VM size is now a bottleneck that can result in capacity errors and an outage. You’re left juggling trade-offs: Do you overprovision SKUs “just in case” to ensure availability? Or risk underprovisioning and inability to scale? AKS offers two solutions that aim to address these capacity scaling challenges.
+
+---
+
+## Breaking the Mold: Features That Change the Game
+
+### Node auto provisioning (NAP): Smarter Scaling
+NAP offers a more intelligent scaling experience. Instead of you guessing the right VM size, NAP uses **pending pod resource requests** to dynamically provision nodes that fit your workloads. Built on the open-source **Karpenter** project, NAP:
+
+- **Automates VM selection**: Chooses optimal SKUs based on CPU, memory, and constraints.
+- **Consolidates intelligently**: Removes underutilized nodes, reducing cost.
+- **Adapts in real time**: Responds to pod pressure without manual intervention.
+
+Think of NAP as Kubernetes with foresight: provisioning what you need, when you need it, without the spreadsheet gymnastics. Without NAP, a single unavailable VM SKU can block scaling entirely. With NAP, AKS dynamically adapts to capacity fluctuations, ensuring workloads keep running on available VM sizes, even during regional/zonal shortages. 
+
+#### How NAP handles capacity errors
+
+When a requested VM SKU isn’t available due to regional or zonal capacity constraints, NAP doesn’t fail outright. Instead, NAP will automatically:
+
+* Evaluate pending pod resource requirements (CPU, memory, GPU, etc.).
+* Check if pending pods can fit on existing nodes
+* Search across multiple VM SKUs within the allowed families defined in your NAP configuration files (custom resource definitions referred to as the NodePool and AKSNodeClass CRDs).
+* Provision an alternative SKU that meets the workload requirements and policy constraints.
+* In the event that no VM sizes that match your requirements are available, NAP will only then send an error detailing that "No available SKU that meets your configuration definition is available".  **Mitigation**: Make sure you reference a broad range of size options in the NAP configuration files (e.g. D-series, multiple SKU families)
+
+This flexibility is key to avoiding hard failures during scale-out.
+
+For more on enabling NAP on your cluster, visit our [NAP documentation](https://learn.microsoft.com/azure/aks/node-auto-provisioning) as well as our docs on configuring the [NodePool CRD](https://learn.microsoft.com/azure/aks/node-auto-provisioning-node-pools) and [AKSNodeClass CRD](https://learn.microsoft.com/azure/aks/node-auto-provisioning-aksnodeclass)
+
+### Virtual machine node pools: Flexibility at scale
+Traditional node pools are rigid: one SKU per pool. Virtual Machine node pools break that limitation. With multi-SKU support, you can:
+
+* Mix VM sizes within a single pool for diverse workloads.
+* Fine-tune capacity without creating dozens of pools.
+* Reduce operational overhead while improving resilience.
+
+This isn’t just flexibility - it’s versatility in capacity-constrained regions.
+
+#### How virtual machine node pools handle capacity errors
+
+You can manually add or update alternative VM SKUs into your new or existing node pools. When a requested VM SKU isn't available due to a regional or zonal capacity constraint, you will receive a capacity error, and can resolve this error by simply adding and updating the VM SKUs in your node pools.
+
+For more on enabling Virtual Machine node pools on your cluster, visit our [Virtual Machine node pools documentation](https://learn.microsoft.com/azure/aks/virtual-machines-node-pools).
+
+## Quick guidance: When to Use What
+Generally, using NAP or Virtual Machine node pools are mutually exclusive. You can use NAP to create standalone VMs which NAP manages instead of traditional node pools, which allows for **mixed SKU autoscaling**. Virtual Machine node pools uses traditional node pools, but allows for **mixed SKU manual scaling**.
+
+* (Recommended) Choose NAP for dynamic environments where manual SKU planning is impractical.
+* Choose Virtual Machine node pools when you need fine-tuned control with exact VM SKUs for compliance, predictable performance, or cost modeling.
+
+Avoid NAP if you require strict SKU governance or have regulatory constraints that cannot allow for dynamic autoscaling. Avoid VM node pools if you want full automation without manual profiles.
+
+## Best practice for resilience
+
+To maximize NAP's ability to handle capacity errors:
+* Define broad SKU families (e.g., D, E) in your NodePool requirements.
+* Avoid overly restrictive affinity rules. Visit our [affinity rules documentation](https://learn.microsoft.com/azure/aks/operator-best-practices-advanced-scheduler#control-pod-scheduling-using-node-selectors-and-affinity) on best practices. 
+* Enable multiple NodePools with different priorities for fallback. Visit our [NAP Node Pool documentation](https://learn.microsoft.com/azure/aks/node-auto-provisioning-node-pools) for more on configuring the NodePool CRD. 
+
+To maximize Virtual Machine node pool's ability to adapt to capacity errors:
+* Be clear on a list of VM SKUs that can tolerate your workloads. Visit our [Azure VM Sizes documentation](https://learn.microsoft.com/azure/virtual-machines/sizes/overview#list-of-vm-size-families-by-type) for more details.
+* Create virtual machine node pools to offer resiliency to your workloads. Visit our [Virtual machine node pool documentation](https://learn.microsoft.com/azure/aks/virtual-machines-node-pools) on how to add a mixed SKU node pool. 
+
+## Getting started with node auto provisioning
+
+### NAP requirements + limitations
+
+To use node auto-provisioning in AKS, you need the following prerequisites:
+
+- An Azure subscription. If you don't have one, you can [create a free account](https://azure.microsoft.com/free).
+- Azure CLI version 2.76.0 or later. To find the version, run az --version. For more information about installing or upgrading the Azure CLI, see Install Azure CLI.
+
+The following limitations and unsupported features apply to node auto-provisioning in AKS:
+
+- You can't enable NAP on clusters enabled with the cluster autoscaler.
+- Windows node pools aren't supported.
+- IPv6 clusters aren't supported.
+- Service principals aren't supported. You can use either a system-assigned or user-assigned managed identity.
+- Disk Encryption Sets aren't supported yet (scheduled for early 2026).
+- Custom certificate authority (CA) certificates aren't supported.
+- You can't stop a cluster enabled with NAP yet.
+- HTTP proxy isn't supported.
+- You can't change the cluster egress outbound type after you create a cluster enabled with NAP.
+- When creating a NAP cluster in a custom virtual network (VNet), you must use a Standard Load Balancer. The Basic Load Balancer isn't supported.
+
+For more on NAP limitations, visit our [NAP documentation](https://learn.microsoft.com/azure/aks/node-auto-provisioning#limitations-and-unsupported-features).
+
+### Create a new NAP-managed AKS cluster
+
+The following command creates a new NAP-managed AKS cluster by setting the `--node-provisioning-mode` field to `Auto`. This command also sets the network configuration to the recommended Azure CNI Overlay with a Cilium dataplane (optional). View our [NAP networking documentation](https://learn.microsoft.com/azure/aks/node-auto-provisioning-networking#supported-networking-configurations-for-nap) for more on supported CNI options. 
+
+```
+az aks create --name $CLUSTER_NAME --resource-group $RESOURCE_GROUP --node-provisioning-mode Auto --network-plugin azure --network-plugin-mode overlay --network-dataplane cilium
+```
+
+### Update an existing cluster to be a NAP-managed cluster
+
+The following command updates an existing cluster to enable NAP:
+
+```
+az aks update --name $CLUSTER_NAME --resource-group $RESOURCE_GROUP --node-provisioning-mode Auto
+```
+
+### Configure NAP custom resource definitions
+
+NAP uses custom resource definition (CRDs) and your application deployment file requirements for its decision-making around which virtual machines to provision and schedule your workloads to. This includes:
+- NodePool - for setting rules around the range of VM sizes,  capacity type (spot vs. on-demand), compute architecture, availability zones, etc.  
+- AKSNodeClass - for setting rules around certain Azure specific settings such as more detailed networking (virtual networks) setup, node image family type, operating system configurations, and other resource-related definitions. 
+
+Visit our [NAP NodePool Documentation](https://learn.microsoft.com/azure/aks/node-auto-provisioning-node-pools) and [NAP AKSNodeClass documentation](https://learn.microsoft.com/azure/aks/node-auto-provisioning-aksnodeclass) for more on configuring these files. 
+
+### Configure NAP disruption 
+
+NAP uses certain disruption rules to decide when to remove existing nodes when they are empty or underutilized, or even replace them with more cost-efficient compute. You can define how NAP will handle disruption events directly in the NodePool CRD. For more details on configuring NAP disruption policies, visit our [NAP disruption documentation](https://learn.microsoft.com/azure/aks/node-auto-provisioning-disruption).
+
+## Getting started with virtual machine node pools
+
+### Virtual machine node pool requirements + limitations
+
+- [InfiniBand](https://blog.aks.azure.com/2025/04/11/infiniband-on-aks) isn't available.
+- [Node pool snapshot](https://learn.microsoft.com/azure/aks/node-pool-snapshot) isn't supported.
+- All VM sizes selected in a node pool need to be from a similar virtual machine family. For example, you can't mix an N-Series virtual machine type with a D-Series virtual machine type in the same node pool.
+- Virtual Machines node pools allow up to five different virtual machine sizes per node pool.
+- An Azure subscription. If you don't have one, you can [create a free account](https://azure.microsoft.com/free).
+- Azure CLI version 2.73.0 or later installed and configured. To find the version, run `az --version`.
+- This feature requires kubernetes version 1.27 or greater. 
+
+### Create a new AKS cluster with virtual machine node pools
+
+The following example creates a new cluster named myAKSCluster with a Virtual Machines node pool containing two nodes with size "Standard_D4s_v3", and sets the Kubernetes version to 1.31.0:
+
+```
+az aks create --resource-group myResourceGroup --name myAKSCluster --vm-set-type "VirtualMachines" --vm-sizes "Standard_D4s_v3" 
+    --node-count 2 --kubernetes-version 1.31.0
+```
+
+### Add a new virtual machine node pool to an existing cluster
+
+The following example adds a Virtual Machines node pool named myvmpool to the myAKSCluster cluster. The node pool creates a ManualScaleProfile with --vm-sizes set to Standard_D4s_v3 and a --node-count of 3:
+
+```bash
+az aks nodepool add --resource-group myResourceGroup --cluster-name myAKSCluster --name myvmpool --vm-set-type "VirtualMachines" --vm-sizes "Standard_D4s_v3" --node-count 3
+```
+
+### Add another VM size in an existing node pool
+You can add additional ManualScaleProfiles to this existing node pool `myvmpool` to have multiple same-family sizes in the same node pool. The following example adds a manual scale profile to node pool myvmpool in cluster myAKSCluster. The node pool includes two nodes with a VM SKU of Standard_D2s_v3:
+
+```
+az aks nodepool manual-scale add --resource-group myResourceGroup --cluster-name myAKSCluster --name myvmpool --vm-sizes "Standard_D2s_v3" --node-count 2
+```
+With this, the example node pool `myvmpool` now has two VM sizes in the same nodepool:
+- "Standard_D4s_v3" (3 nodes)
+- "Standard_D2s_v3" (2 nodes)
+
+### Update existing node pool size in a virtual machine node pool
+
+You can also update the size and/or node count of existing node pools. The following example updates a manual scale profile in the `myvmpool` node pool in the `myAKSCluster` cluster. The command updates the number of nodes to five and changes the VM SKU from Standard_D4s_v3 to Standard_D8s_v3:
+
+```
+az aks nodepool manual-scale update --resource-group myResourceGroup --cluster-name myAKSCluster --name myvmpool --current-vm-sizes "Standard_D4s_v3" --vm-sizes "Standard_D8s_v3" --node-count 5
+```
+
+For more on managing Virtual Machine node pools, visit our [Virtual Machine node pools documentation](https://learn.microsoft.com/azure/aks/virtual-machines-node-pools).
+
+## What’s next on the AKS roadmap
+
+NAP: Expect deeper integration with cost optimization tools and advanced disruption policies for even smarter consolidation.
+Virtual Machine node pools: Auto-scaling (general availability) is on the horizon, reducing manual configuration and enabling adaptive scaling across mixed SKUs.
+
+## Next steps
+
+Ready to get started?
+
+1. **Try one of these features now:** Follow the [Enable node auto provisioning steps](https://learn.microsoft.com/azure/aks/use-node-auto-provisioning) or [create a Virtual Machine node pool](https://learn.microsoft.com/azure/aks/virtual-machines-node-pools).
+1. **Share feedback:** Open issues or ideas in [AKS GitHub Issues](https://github.com/Azure/AKS/issues).
+1. **Join the community:** Subscribe to the [AKS Community YouTube](https://www.youtube.com/@theakscommunity) and follow [@theakscommunity](https://x.com/theakscommunity) on X.