Feature blog for ReadWriteOncePod GA graduation
Chris Henzie
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layout: blog
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title: "Kubernetes 1.29: Single Pod Access Mode for PersistentVolumes Graduates to Stable"
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date: 2023-12-18
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slug: read-write-once-pod-access-mode-ga
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---
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**Author:** Chris Henzie (Google)
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With the release of Kubernetes v1.29, the `ReadWriteOncePod` volume access mode
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has graduated to general availability: it's part of Kubernetes' stable API. In
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this blog post, I'll take a closer look at this access mode and what it does.
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## What is `ReadWriteOncePod`?
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`ReadWriteOncePod` is an access mode for
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[PersistentVolumes](/docs/concepts/storage/persistent-volumes/#persistent-volumes) (PVs)
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and [PersistentVolumeClaims](/docs/concepts/storage/persistent-volumes/#persistentvolumeclaims) (PVCs)
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introduced in Kubernetes v1.22. This access mode enables you to restrict volume
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access to a single pod in the cluster, ensuring that only one pod can write to
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the volume at a time. This can be particularly useful for stateful workloads
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that require single-writer access to storage.
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For more context on access modes and how `ReadWriteOncePod` works read
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[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)
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in the _Introducing Single Pod Access Mode for PersistentVolumes_ article from 2021.
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## How can I start using `ReadWriteOncePod`?
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The `ReadWriteOncePod` volume access mode is available by default in Kubernetes
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versions v1.27 and beyond. In Kubernetes v1.29 and later, the Kubernetes API
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always recognizes this access mode.
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Note that `ReadWriteOncePod` is
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[only supported for CSI volumes](/docs/concepts/storage/persistent-volumes/#access-modes),
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and before using this feature, you will need to update the following
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[CSI sidecars](https://kubernetes-csi.github.io/docs/sidecar-containers.html)
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to these versions or greater:
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- [csi-provisioner:v3.0.0+](https://github.com/kubernetes-csi/external-provisioner/releases/tag/v3.0.0)
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- [csi-attacher:v3.3.0+](https://github.com/kubernetes-csi/external-attacher/releases/tag/v3.3.0)
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- [csi-resizer:v1.3.0+](https://github.com/kubernetes-csi/external-resizer/releases/tag/v1.3.0)
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To start using `ReadWriteOncePod`, you need to create a PVC with the
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`ReadWriteOncePod` access mode:
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```yaml
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kind: PersistentVolumeClaim
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apiVersion: v1
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metadata:
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name: single-writer-only
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spec:
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accessModes:
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- ReadWriteOncePod # Allows only a single pod to access single-writer-only.
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resources:
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requests:
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storage: 1Gi
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```
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If your storage plugin supports
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[Dynamic provisioning](/docs/concepts/storage/dynamic-provisioning/), then
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new PersistentVolumes will be created with the `ReadWriteOncePod` access mode
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applied.
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Read [Migrating existing PersistentVolumes](/blog/2021/09/13/read-write-once-pod-access-mode-alpha/#migrating-existing-persistentvolumes)
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for details on migrating existing volumes to use `ReadWriteOncePod`.
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## How can I learn more?
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Please see the blog posts [alpha](/blog/2021/09/13/read-write-once-pod-access-mode-alpha),
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[beta](/blog/2023/04/20/read-write-once-pod-access-mode-beta), and
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[KEP-2485](https://github.com/kubernetes/enhancements/blob/master/keps/sig-storage/2485-read-write-once-pod-pv-access-mode/README.md)
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for more details on the `ReadWriteOncePod` access mode and motivations for CSI
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spec changes.
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## How do I get involved?
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The [Kubernetes #csi Slack channel](https://kubernetes.slack.com/messages/csi)
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and any of the standard
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[SIG Storage communication channels](https://github.com/kubernetes/community/blob/master/sig-storage/README.md#contact)
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are great methods to reach out to the SIG Storage and the CSI teams.
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Special thanks to the following people whose thoughtful reviews and feedback helped shape this feature:
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* Abdullah Gharaibeh (ahg-g)
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* Aldo Culquicondor (alculquicondor)
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* Antonio Ojea (aojea)
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* David Eads (deads2k)
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* Jan Šafránek (jsafrane)
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* Joe Betz (jpbetz)
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* Kante Yin (kerthcet)
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* Michelle Au (msau42)
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* Tim Bannister (sftim)
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* Xing Yang (xing-yang)
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If you’re interested in getting involved with the design and development of CSI
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or any part of the Kubernetes storage system, join the
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[Kubernetes Storage Special Interest Group](https://github.com/kubernetes/community/tree/master/sig-storage) (SIG).
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We’re rapidly growing and always welcome new contributors.
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