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Feature blog for ReadWriteOncePod GA graduation
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content/en/blog/_posts/2023-12-18-read-write-once-pod-access-mode-ga.md
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--- | ||
layout: blog | ||
title: "Kubernetes 1.29: Single Pod Access Mode for PersistentVolumes Graduates to Stable" | ||
date: 2023-12-18 | ||
slug: read-write-once-pod-access-mode-ga | ||
--- | ||
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**Author:** Chris Henzie (Google) | ||
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With the release of Kubernetes v1.29, the `ReadWriteOncePod` volume access mode | ||
has graduated to general availability: it's part of Kubernetes' stable API. In | ||
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 | ||
[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. | ||
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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. | ||
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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 | ||
versions v1.27 and beyond. In Kubernetes v1.29 and later, the Kubernetes API | ||
always recognizes this access mode. | ||
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Note that `ReadWriteOncePod` is | ||
[only supported for CSI volumes](/docs/concepts/storage/persistent-volumes/#access-modes), | ||
and 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: | ||
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- [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) | ||
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To start using `ReadWriteOncePod`, you need to create a PVC with the | ||
`ReadWriteOncePod` access mode: | ||
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```yaml | ||
kind: PersistentVolumeClaim | ||
apiVersion: v1 | ||
metadata: | ||
name: single-writer-only | ||
spec: | ||
accessModes: | ||
- ReadWriteOncePod # Allows 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/), then | ||
new PersistentVolumes will be created with the `ReadWriteOncePod` access mode | ||
applied. | ||
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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`. | ||
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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), | ||
[beta](/blog/2023/04/20/read-write-once-pod-access-mode-beta), 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. | ||
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## How do I get involved? | ||
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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 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) | ||
* 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) | ||
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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. |