Merge pull request #54021 from torredil/main

sig-storage: Mutable CSI Node Allocatable Blog Graduates to GA

Author: k8s-ci-robot

content/en/blog/_posts/2026-01-14-mutable-csi-node-allocatable-ga.md

@@ -0,0 +1,110 @@
+---
+layout: blog
+title: "Kubernetes v1.36: Mutable CSI Node Allocatable Graduates to GA"
+date: 2026-01-14T10:30:00-08:00
+slug: kubernetes-v1-36-mutable-csi-node-allocatable-ga
+draft: true
+author: Eddie Torres (Amazon Web Services)
+---
+
+On behalf of Kubernetes SIG Storage, I am pleased to announce that the
+_mutable CSI node allocatable count_ feature has graduated to General
+Availability (GA) in Kubernetes v1.36!
+
+This feature, first introduced as alpha in Kubernetes v1.33 and promoted to beta in
+v1.34, allows [Container Storage Interface
+(CSI)](https://kubernetes-csi.github.io/docs/introduction.html) drivers to
+dynamically update the reported maximum number of volumes that a node can handle.
+This capability significantly enhances the accuracy of pod scheduling decisions
+and reduces scheduling failures caused by outdated volume capacity information.
+
+## Background
+
+Traditionally, Kubernetes CSI drivers report a static maximum volume attachment
+limit when initializing. However, actual attachment capacities can change during
+a node's lifecycle for various reasons, such as:
+
+- Manual or external operations attaching/detaching volumes outside of Kubernetes control.
+- Dynamically attached network interfaces or specialized hardware (GPUs, NICs,
+  etc.) consuming available slots.
+- Multi-driver scenarios, where one CSI driver's operations affect available
+  capacity reported by another.
+
+Static reporting can cause Kubernetes to schedule pods onto nodes that appear to
+have capacity but don't, leading to pods stuck in a `ContainerCreating` state.
+
+## Dynamically adapting CSI volume limits
+
+With this feature now GA, Kubernetes enables CSI drivers to dynamically adjust
+and report node attachment capacities at runtime. This ensures that the
+scheduler, as well as other components relying on this information, have the
+most accurate, up-to-date view of node capacity.
+
+### How it works
+
+Kubernetes supports two mechanisms for updating the reported node volume limits:
+
+- **Periodic Updates:** CSI drivers specify an interval to periodically refresh
+  the node's allocatable capacity.
+- **Reactive Updates:** An immediate update triggered when a volume attachment
+  fails due to exhausted resources (`ResourceExhausted` error).
+
+### Example CSI driver configuration
+
+Below is an example of configuring a CSI driver to enable periodic updates every 60 seconds:
+
+```yaml
+apiVersion: storage.k8s.io/v1
+kind: CSIDriver
+metadata:
+  name: example.csi.k8s.io
+spec:
+  nodeAllocatableUpdatePeriodSeconds: 60
+```
+
+This configuration directs kubelet to periodically call the CSI driver's
+`NodeGetInfo` method every 60 seconds, updating the node's allocatable volume
+count. Kubernetes enforces a minimum update interval of 10 seconds to balance
+accuracy and resource usage.
+
+### Immediate updates on attachment failures
+
+When a volume attachment operation fails due to a `ResourceExhausted` error
+(gRPC code `8`), Kubernetes immediately updates the allocatable count instead of
+waiting for the next periodic update. The kubelet then marks the affected pods
+as Failed, enabling their controllers to recreate them. This prevents pods from
+getting permanently stuck in the `ContainerCreating` state.
+
+## What's new in GA
+
+With the graduation to GA in Kubernetes v1.36, the
+`MutableCSINodeAllocatableCount` feature gate is unconditionally enabled
+and cannot be disabled. For any cluster running Kubernetes v1.36 or
+later:
+
+- The `.spec.drivers[*].allocatable.count` field of a CSINode is
+  mutable.
+- The `nodeAllocatableUpdatePeriodSeconds` field is available in the
+  CSIDriver spec.
+
+## Getting started
+
+To take advantage of this feature in your Kubernetes v1.36 cluster:
+
+1. Update your CSI driver configuration by setting
+   `nodeAllocatableUpdatePeriodSeconds` to your desired update interval.
+2. Monitor and observe improvements in scheduling accuracy and pod placement reliability.
+
+## References
+
+- [KEP-4876: Mutable CSI Node Allocatable Count](https://kep.k8s.io/4876)
+- [Alpha Release Blog (v1.33)](/blog/2025/05/02/kubernetes-1-33-mutable-csi-node-allocatable-count/)
+- [Beta Release Blog (v1.34)](/blog/2025/09/11/kubernetes-v1-34-mutable-csi-node-allocatable-count/)
+
+## Getting involved
+
+This feature was driven by the [SIG
+Storage](https://github.com/kubernetes/community/tree/master/sig-storage)
+community. Please join us to connect with the community and share your ideas
+and feedback around the above feature and beyond. We look forward to hearing
+from you!