Kubernetes PV在Retain策略Released状态下重新分配到PVC恢复数据

[TOC]

1. 实验目的和环境说明

原由：在使用helm update stable/sonatype-nexus从1.6版本更新到1.13版本后，出现PVC删除，重新创建PVC的情况，好在原来PV为Retain。故研究下Retain的PV怎么恢复数据。

实验目的：PVC删除后，PV因Retain策略，状态为Released，将PV内数据恢复成PVC，挂载到POD内，达到数据恢复。

环境说明：

• Kubernetes: 1.12.1
• StorageClass: ceph-rbd
• OS: CentOS7

2. 实验过程

准备yaml文件：

pvc.yaml

apiVersion: v1kind: PersistentVolumeClaimmetadata: ?name: pvc-testspec: ?accessModes: ???- ReadWriteOnce ?storageClassName: ceph-rbd ??resources: ???requests: ?????storage: 1Gi

nginx.yaml

apiVersion: extensions/v1beta1kind: Deploymentmetadata: ?name: nginx-rbdspec: ?replicas: 1 ?template: ???metadata: ?????labels: ???????name: nginx ???spec: ?????containers: ???????- name: nginx ?????????image: nginx ?????????imagePullPolicy: IfNotPresent ?????????ports: ???????????- containerPort: 80 ?????????volumeMounts: ???????????- name: ceph-rbd-volume ?????????????mountPath: "/usr/share/nginx/html" ?????volumes: ?????- name: ceph-rbd-volume ???????persistentVolumeClaim: ?????????claimName: pvc-test

新建pvc、deployment、写入数据并删除pvc操作过程：

[root@lab1 test]# lltotal 8-rw-r--r-- 1 root root 533 Oct 24 17:54 nginx.yaml-rw-r--r-- 1 root root 187 Oct 24 17:55 pvc.yaml[root@lab1 test]# kubectl apply -f pvc.yaml persistentvolumeclaim/pvc-test created[root@lab1 test]# kubectl get pvc NAME ??????????????STATUS ??VOLUME ????????????????????????????????????CAPACITY ??ACCESS MODES ??STORAGECLASS ??AGEpvc-test ??????????Bound ???pvc-069c4486-d773-11e8-bd12-000c2931d938 ??1Gi ???????RWO ???????????ceph-rbd ??????7s[root@lab1 test]# kubectl apply -f nginx.yaml deployment.extensions/nginx-rbd created[root@lab1 test]# kubectl get pod |grep nginx-rbdnginx-rbd-7c6449886-thv25 ??????????1/1 ????Running ??0 ?????????33s[root@lab1 test]# kubectl exec -it nginx-rbd-7c6449886-thv25 -- /bin/bash -c ‘echo ygqygq2 > /usr/share/nginx/html/ygqygq2.html‘ ???????[root@lab1 test]# kubectl exec -it nginx-rbd-7c6449886-thv25 -- cat /usr/share/nginx/html/ygqygq2.htmlygqygq2[root@lab1 test]# kubectl delete -f nginx.yaml deployment.extensions "nginx-rbd" deleted[root@lab1 test]# kubectl get pvc pvc-test ????NAME ??????STATUS ??VOLUME ????????????????????????????????????CAPACITY ??ACCESS MODES ??STORAGECLASS ??AGEpvc-test ??Bound ???pvc-069c4486-d773-11e8-bd12-000c2931d938 ??1Gi ???????RWO ???????????ceph-rbd ??????4m10s[root@lab1 test]# kubectl delete pvc pvc-test ?# 删除PVCpersistentvolumeclaim "pvc-test" deleted[root@lab1 test]# kubectl get pv pvc-069c4486-d773-11e8-bd12-000c2931d938NAME ??????????????????????????????????????CAPACITY ??ACCESS MODES ??RECLAIM POLICY ??STATUS ????CLAIM ?????????????STORAGECLASS ??REASON ??AGEpvc-069c4486-d773-11e8-bd12-000c2931d938 ??1Gi ???????RWO ???????????Retain ??????????Released ??default/pvc-test ??ceph-rbd ???????????????4m33s[root@lab1 test]# kubectl get pv pvc-069c4486-d773-11e8-bd12-000c2931d938 -o yaml > /tmp/pvc-069c4486-d773-11e8-bd12-000c2931d938.yaml ?# 保留备用

从上面可以看到，pvc删除后，pv变成Released状态。

再次创建同名PVC，查看是否分配原来PV操作过程：

[root@lab1 test]# kubectl apply -f pvc.yaml persistentvolumeclaim/pvc-test created[root@lab1 test]# kubectl get pvc ?# 查看新建的PVC ?????????????NAME ??????????????STATUS ??VOLUME ????????????????????????????????????CAPACITY ??ACCESS MODES ??STORAGECLASS ??AGEpvc-test ??????????Bound ???pvc-f2df48ea-d773-11e8-b6c8-000c29ea3e30 ??1Gi ???????RWO ???????????ceph-rbd ??????19s[root@lab1 test]# kubectl get pv pvc-069c4486-d773-11e8-bd12-000c2931d938 ?# 查看原来的PVNAME ??????????????????????????????????????CAPACITY ??ACCESS MODES ??RECLAIM POLICY ??STATUS ????CLAIM ?????????????STORAGECLASS ??REASON ??AGEpvc-069c4486-d773-11e8-bd12-000c2931d938 ??1Gi ???????RWO ???????????Retain ??????????Released ??default/pvc-test ??ceph-rbd ???????????????7m18s[root@lab1 test]# 

从上面可以看到，PVC分配的是新的PV，因为PV状态不是Available。

那怎么才能让PV状态变成Available呢？我们来查看之前的PV：

[root@lab1 test]# cat /tmp/pvc-069c4486-d773-11e8-bd12-000c2931d938.yamlapiVersion: v1kind: PersistentVolumemetadata: ?annotations: ???pv.kubernetes.io/provisioned-by: ceph.com/rbd ???rbdProvisionerIdentity: ceph.com/rbd ?creationTimestamp: 2018-10-24T09:56:06Z ?finalizers: ?- kubernetes.io/pv-protection ?name: pvc-069c4486-d773-11e8-bd12-000c2931d938 ?resourceVersion: "11752758" ?selfLink: /api/v1/persistentvolumes/pvc-069c4486-d773-11e8-bd12-000c2931d938 ?uid: 06b57ef7-d773-11e8-bd12-000c2931d938spec: ?accessModes: ?- ReadWriteOnce ?capacity: ???storage: 1Gi ?claimRef: ???apiVersion: v1 ???kind: PersistentVolumeClaim ???name: pvc-test ???namespace: default ???resourceVersion: "11751559" ???uid: 069c4486-d773-11e8-bd12-000c2931d938 ?persistentVolumeReclaimPolicy: Retain ?rbd: ???fsType: ext4 ???image: kubernetes-dynamic-pvc-06a25bd3-d773-11e8-8c3e-0a580af400d5 ???keyring: /etc/ceph/keyring ???monitors: ???- 192.168.105.92:6789 ???- 192.168.105.93:6789 ???- 192.168.105.94:6789 ???pool: kube ???secretRef: ?????name: ceph-secret ?????namespace: kube-system ???user: kube ?storageClassName: ceph-rbdstatus: ?phase: Released

从上面可以看到，spec.claimRef这段，仍保留之前的PVC信息。

我们大胆删除spec.claimRef这段。再次查看PV：

kubectl edit pv pvc-069c4486-d773-11e8-bd12-000c2931d938

[root@lab1 test]# kubectl get pv pvc-069c4486-d773-11e8-bd12-000c2931d938 NAME ??????????????????????????????????????CAPACITY ??ACCESS MODES ??RECLAIM POLICY ??STATUS ?????CLAIM ??STORAGECLASS ??REASON ??AGEpvc-069c4486-d773-11e8-bd12-000c2931d938 ??1Gi ???????RWO ???????????Retain ??????????Available ??????????ceph-rbd ???????????????10m

从上面可以看到，之前的PV pvc-069c4486-d773-11e8-bd12-000c2931d938已经变为Available。

再次创建PVC、deployment，并查看数据：

new_pvc.yaml

apiVersion: v1kind: PersistentVolumeClaimmetadata: ?name: pvc-test-newspec: ?accessModes: ???- ReadWriteOnce ?storageClassName: ceph-rbd ??resources: ???requests: ?????storage: 1Gi

new_nginx.yaml

apiVersion: extensions/v1beta1kind: Deploymentmetadata: ?name: nginx-rbdspec: ?replicas: 1 ?template: ???metadata: ?????labels: ???????name: nginx ???spec: ?????containers: ???????- name: nginx ?????????image: nginx ?????????imagePullPolicy: IfNotPresent ?????????ports: ???????????- containerPort: 80 ?????????volumeMounts: ???????????- name: ceph-rbd-volume ?????????????mountPath: "/usr/share/nginx/html" ?????volumes: ?????- name: ceph-rbd-volume ???????persistentVolumeClaim: ?????????claimName: pvc-test-new

操作过程：

[root@lab1 test]# kubectl apply -f new_pvc.yaml persistentvolumeclaim/pvc-test-new created[root@lab1 test]# kubectl get pvc NAME ??????????????STATUS ??VOLUME ????????????????????????????????????CAPACITY ??ACCESS MODES ??STORAGECLASS ??AGEpvc-test ??????????Bound ???pvc-f2df48ea-d773-11e8-b6c8-000c29ea3e30 ??1Gi ???????RWO ???????????ceph-rbd ??????31mpvc-test-new ??????Bound ???pvc-069c4486-d773-11e8-bd12-000c2931d938 ??1Gi ???????RWO ???????????ceph-rbd ??????27m[root@lab1 test]# kubectl apply -f new_nginx.yaml [root@lab1 test]# kubectl get pod|grep nginx-rbdnginx-rbd-79bb766b6c-mv2h8 ?????????1/1 ????Running ??0 ?????????20m[root@lab1 test]# kubectl exec -it nginx-rbd-79bb766b6c-mv2h8 -- ls /usr/share/nginx/htmllost+found ?ygqygq2.html[root@lab1 test]# kubectl exec -it nginx-rbd-79bb766b6c-mv2h8 -- cat /usr/share/nginx/html/ygqygq2.htmlygqygq2

从上面可以看到，新的PVC分配到的是原来的PV pvc-069c4486-d773-11e8-bd12-000c2931d938，并且数据完全还在。

3. 小结

当前版本Kubernetes PVC存储大小是唯一能被设置或请求的资源，因我们没有修改PVC的大小，在PV的Available状态下，有PVC请求分配相同大小时，PV会被分配出去并绑定成功。 ????
在PV变成Available过程中，最关键的是PV的spec.claimRef字段，该字段记录着原来PVC的绑定信息，删除绑定信息，即可重新释放PV从而达到Available。

参考资料：
[1] https://kubernetes.io/docs/concepts/storage/persistent-volumes/
[2] https://kubernetes.io/docs/concepts/storage/storage-classes/
[3] http://dockone.io/article/2082
[4] http://dockone.io/article/2087

Kubernetes PV在Retain策略Released状态下重新分配到PVC恢复数据

原文地址：http://blog.51cto.com/ygqygq2/2308576