Merge pull request #39817 from chrishenzie/read-write-once-pod-beta

Feature blog for ReadWriteOncePod beta graduation

Author: k8s-ci-robot

content/en/blog/_posts/2023-04-20-read-write-once-pod-access-mode-beta.md

@@ -0,0 +1,105 @@
+---
+layout: blog
+title: "Kubernetes 1.27: Single Pod Access Mode for PersistentVolumes Graduates to Beta"
+date: 2023-04-20
+slug: read-write-once-pod-access-mode-beta
+---
+
+**Author:** Chris Henzie (Google)
+
+With the release of Kubernetes v1.27 the ReadWriteOncePod feature has graduated
+to beta. In this blog post, we'll take a closer look at this feature, what it
+does, and how it has evolved in the beta release.
+
+## What is ReadWriteOncePod?
+
+ReadWriteOncePod is a new access mode for
+[PersistentVolumes](/docs/concepts/storage/persistent-volumes/#persistent-volumes) (PVs)
+and [PersistentVolumeClaims](/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims) (PVCs)
+introduced in Kubernetes v1.22. This access mode enables you to restrict volume
+access to a single pod in the cluster, ensuring that only one pod can write to
+the volume at a time. This can be particularly useful for stateful workloads
+that require single-writer access to storage.
+
+For more context on access modes and how ReadWriteOncePod works read
+[What are access modes and why are they important?](/blog/2021/09/13/read-write-once-pod-access-mode-alpha/#what-are-access-modes-and-why-are-they-important)
+in the _Introducing Single Pod Access Mode for PersistentVolumes_ article from 2021.
+
+## Changes in the ReadWriteOncePod beta
+
+The ReadWriteOncePod beta adds support for
+[scheduler preemption](/docs/concepts/scheduling-eviction/pod-priority-preemption/)
+of pods using ReadWriteOncePod PVCs.
+
+Scheduler preemption allows higher-priority pods to preempt lower-priority pods,
+so that they can start running on the same node. With this release, pods using
+ReadWriteOncePod PVCs can also be preempted if a higher-priority pod requires
+the same PVC.
+
+## How can I start using ReadWriteOncePod?
+
+With ReadWriteOncePod now in beta, it will be enabled by default in cluster
+versions v1.27 and beyond.
+
+Note that ReadWriteOncePod is
+[only supported for CSI volumes](/docs/concepts/storage/persistent-volumes/#access-modes).
+Before using this feature you will need to update the following
+[CSI sidecars](https://kubernetes-csi.github.io/docs/sidecar-containers.html)
+to these versions or greater:
+
+- [csi-provisioner:v3.0.0+](https://github.com/kubernetes-csi/external-provisioner/releases/tag/v3.0.0)
+- [csi-attacher:v3.3.0+](https://github.com/kubernetes-csi/external-attacher/releases/tag/v3.3.0)
+- [csi-resizer:v1.3.0+](https://github.com/kubernetes-csi/external-resizer/releases/tag/v1.3.0)
+
+To start using ReadWriteOncePod, create a PVC with the ReadWriteOncePod access mode:
+
+```yaml
+kind: PersistentVolumeClaim
+apiVersion: v1
+metadata:
+  name: single-writer-only
+spec:
+  accessModes:
+  - ReadWriteOncePod # Allow only a single pod to access single-writer-only.
+  resources:
+    requests:
+      storage: 1Gi
+```
+
+If your storage plugin supports
+[dynamic provisioning](/docs/concepts/storage/dynamic-provisioning/),
+new PersistentVolumes will be created with the ReadWriteOncePod access mode applied.
+
+Read [Migrating existing PersistentVolumes](/blog/2021/09/13/read-write-once-pod-access-mode-alpha/#migrating-existing-persistentvolumes)
+for details on migrating existing volumes to use ReadWriteOncePod.
+
+## How can I learn more?
+
+Please see the [alpha blog post](/blog/2021/09/13/read-write-once-pod-access-mode-alpha)
+and [KEP-2485](https://github.com/kubernetes/enhancements/blob/master/keps/sig-storage/2485-read-write-once-pod-pv-access-mode/README.md)
+for more details on the ReadWriteOncePod access mode and motivations for CSI spec changes.
+
+## How do I get involved?
+
+The [Kubernetes #csi Slack channel](https://kubernetes.slack.com/messages/csi)
+and any of the standard
+[SIG Storage communication channels](https://github.com/kubernetes/community/blob/master/sig-storage/README.md#contact)
+are great mediums to reach out to the SIG Storage and the CSI teams.
+
+Special thanks to the following people whose thoughtful reviews and feedback helped shape this feature:
+
+* Abdullah Gharaibeh (ahg-g)
+* Aldo Culquicondor (alculquicondor)
+* Antonio Ojea (aojea)
+* David Eads (deads2k)
+* Jan Šafránek (jsafrane)
+* Joe Betz (jpbetz)
+* Kante Yin (kerthcet)
+* Michelle Au (msau42)
+* Tim Bannister (sftim)
+* Xing Yang (xing-yang)
+
+If you’re interested in getting involved with the design and development of CSI
+or any part of the Kubernetes storage system, join the
+[Kubernetes Storage Special Interest Group](https://github.com/kubernetes/community/tree/master/sig-storage) (SIG).
+We’re rapidly growing and always welcome new contributors.