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144 lines
5.2 KiB
Markdown
144 lines
5.2 KiB
Markdown
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# In-tree storage plugin to CSI Driver Migration
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This document covers the example usage of in-tree RBD storage plugin to CSI
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migration feature which can be enabled in a Kubernetes cluster. At present, this
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feature is only supported for RBD in-tree plugin. Once this feature is enabled,
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the in-tree volume requests (`kubernetes.io/rbd`) will be redirected to a
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corresponding CSI (`rbd.csi.ceph.com`) driver.
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## RBD
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- [Prerequisite](#prerequisite)
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- [Volume operations after enabling CSI migration](#volume-operations-after-enabling-csi-migration)
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- [Create volume](#create-volume)
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- [Mount volume to a POD](#mount-volume-to-a-pod)
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- [Resize volume](#resize-volume)
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- [Unmount volume](#unmount-volume)
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- [Delete volume](#delete-volume)
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- [References](#additional-references)
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### Prerequisite
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For in-tree RBD migration to CSI driver to be supported for your Kubernetes
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cluster, the Kubernetes version running in your cluster should be >= v1.23. We
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also need sidecar controllers (`csi-provisioner` and `csi-resizer`) which are
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compatible with the Kubernetes version v1.23 to be available in your cluster.
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You can enable the migration with a couple of feature gates in your Kubernetes
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cluster. These feature gates are alpha in Kubernetes 1.23 release.
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- `CSIMigrationRBD`: when enabled, it will redirect traffic from in-tree rbd
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plugin (`kubernetes.io/rbd`) to CSI driver (`rbd.csi.ceph.com`), default
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to `false` now.
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- `IntreePluginRBDUnregister`: Disables the RBD in-tree driver
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To enable feature gates, refer [feature gates](https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/)
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As a Kubernetes cluster operator that administers storage, here are the
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prerequisites that you must complete before you attempt migration to the RBD CSI
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driver:
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- You must install the Ceph CSI driver (`rbd.csi.ceph.com`), v3.5.0 or above,
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into your Kubernetes cluster.
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- Configure `clusterID` field in the configmap as
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discussed [here](https://github.com/ceph/ceph-csi/blob/devel/docs/design/proposals/intree-migrate.md#clusterid-field-in-the-migration-request)
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- Configure migration secret as
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discussed [here](https://github.com/ceph/ceph-csi/blob/devel/docs/design/proposals/intree-migrate.md#migration-secret-for-csi-operations)
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In below examples, `fast-rbd` is in-tree storageclass with provisioner
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referencing in-tree provisioner `Kubernetes.io/rbd`.
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```console
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$ kubectl describe sc fast-rbd |grep -i provisioner
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Provisioner: Kubernetes.io/rbd
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```
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### Volume operations after enabling CSI migration
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This section covers the operations on volumes provisioned after enabling CSI
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migration in a cluster.
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#### Create Volume
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``` console
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$ kubectl create -f pvc.yaml
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persistentvolumeclaim/testpvc created
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$ kubectl get pvc,pv
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NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
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persistentvolumeclaim/testpvc Bound pvc-c4e7dca5-4be6-4168-8eb5-af6ade04261f 1Gi RWO fast-rbd 24s
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NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
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persistentvolume/pvc-c4e7dca5-4be6-4168-8eb5-af6ade04261f 1Gi RWO Delete Bound default/testpvc fast-rbd 18s
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```
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#### Mount Volume to a POD
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Create a pod with PVC and verify the mount inside the POD
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```console
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$ kubectl create -f pod.yaml
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pod/task-pv-pod created
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$ kubectl get pods
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NAME READY STATUS RESTARTS AGE
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task-pv-pod 1/1 Running 0 2m36s
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$ kubectl get pvc
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NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
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testpvc Bound pvc-c4e7dca5-4be6-4168-8eb5-af6ade04261f 1Gi RWO fast-rbd 4m40s
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$ kubectl exec -ti task-pv-pod -- df -kh |grep nginx
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/dev/rbd0 976M 2.6M 958M 1% /usr/share/nginx/html
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```
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#### Resize Volume
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Resize PVC from 1Gi to 2Gi and verify the new size change in the POD
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```console
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$ kubectl patch pvc testpvc -p '{"spec":{"resources":{"requests":{"storage":"2Gi"}}}}}'
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persistentvolumeclaim/testpvc patched
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$ kubectl exec -ti task-pv-pod -- df -kh |grep nginx
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/dev/rbd0 2.0G 3.0M 2.0G 1% /usr/share/nginx/html
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```
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#### Unmount Volume
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Delete POD and verify pod deleted successfully
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```console
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$ kubectl get pods
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NAME READY STATUS RESTARTS AGE
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task-pv-pod 1/1 Running 0 5m31s
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$ kubectl delete pod task-pv-pod
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pod "task-pv-pod" deleted
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$ kubectl get pods
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```
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#### Delete volume
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Delete PVC and verify PVC and PV objects are deleted
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```console
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$ kubectl delete pvc testpvc
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persistentvolumeclaim "testpvc" deleted
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$ kubectl get pvc
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No resources found in default namespace.
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$ kubectl get pv
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No resources found
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```
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### Additional References
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To know more about in-tree to CSI migration:
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- [design doc](./design/proposals/intree-migrate.md)
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- [Kubernetes 1.17 Feature: Kubernetes In-Tree to CSI Volume Migration Moves to Beta](https://Kubernetes.io/blog/2019/12/09/Kubernetes-1-17-feature-csi-migration-beta/)
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