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kubernetes中用NFS做后端存储支不支持PVC扩容?

作者:互联网

kubernetes中用NFS做后端存储支不支持PVC扩容?

在虚拟机时代,我们经常会收到给磁盘扩容的需求,一般我们就是添加一块磁盘,然后做LVM扩容操作,那在容器时代,我们可以给PVC扩容吗?

之前发了持久化存储相关的知识--PV和PVC,StorageClass,本文来给你介绍一下用NFS做后端存储能不能扩容的问题,当然在生产上没有哪个愿意用NFS做后端存储......

你首先需要准备好NFS存储

首先我们介绍一下pv和pvc模式,也就是纯手动创建的模式。
(1)、首先我们创建一个PV的YAML文件(pv2.yaml)

apiVersion: v1

kind: PersistentVolume

metadata:

  name: my-pv02

  labels:

    storage: pv

spec:

  accessModes:

  - ReadWriteOnce

  capacity:

    storage: 500Mi

  persistentVolumeReclaimPolicy: Recycle

  nfs:

    path: /data/k8s

    server: 10.1.10.128

创建pv

# kubectl apply -f pv2.yaml

persistentvolume/my-pv02 created

#  kubectl get pv

NAME      CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM              STORAGECLASS   REASON   AGE                                        30s

my-pv02   500Mi      RWO            Recycle          Bound       default/pvc-test                           30s

(2)、创建PVC(pvc.yaml),我们这里创建一个比较小的pvc,如下

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: pvc-test

spec:

  accessModes:

  - ReadWriteOnce

  resources:

    requests:

      storage: 500Mi

然后创建pvc

# kubectl apply -f pvc.yaml

# kubectl get pvc

NAME       STATUS   VOLUME    CAPACITY   ACCESS MODES   STORAGECLASS   AGE

pvc-test   Bound    my-pv02   500Mi      RWO                           58s

我们其实可以看到,我在pvc里定义的是500Mi,它会自动匹配刚好合适的PV。
这时候如果我们修改my-pv02的YAML文件,如下:

apiVersion: v1

kind: PersistentVolume

metadata:

  name: my-pv02

  labels:

    storage: pv

spec:

  accessModes:

  - ReadWriteOnce

  capacity:

    storage: 2Gi

  persistentVolumeReclaimPolicy: Recycle

  nfs:

    path: /data/k8s

    server: 10.1.10.128

然后我们尝试创建这个PV,如下:

# kubectl apply -f pv2.yaml

persistentvolume/my-pv02 configured

# kubectl get pv

NAME      CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM              STORAGECLASS   REASON   AGE

my-pv02   2Gi        RWO            Recycle          Bound       default/pvc-test                           116m

# kubectl get pvc

NAME       STATUS   VOLUME    CAPACITY   ACCESS MODES   STORAGECLASS   AGE

pvc-test   Bound    my-pv02   500Mi      RWO                           116m

我们看到我们my-pv02的CAPACITY变成了2Gi,我们的pvc还是500Mi,那么我们能不能对PVC进行扩容呢?我尝试的修改了pvc的配置文件,如下:

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: pvc-test

spec:

  accessModes:

  - ReadWriteOnce

  resources:

    requests:

      storage: 1Gi 

然后我们执行这个配置文件

]# kubectl apply -f  pvc.yaml

Error from server (Forbidden): error when applying patch:

{"metadata":{"annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"PersistentVolumeClaim\",\"metadata\":{\"annotations\":{},\"name\":\"pvc-test\",\"namespace\":\"default\"},\"spec\":{\"accessModes\":[\"ReadWriteOnce\"],\"resources\":{\"requests\":{\"storage\":\"1Gi\"}}}}\n"}},"spec":{"resources":{"requests":{"storage":"1Gi"}}}}

to:

Resource: "/v1, Resource=persistentvolumeclaims", GroupVersionKind: "/v1, Kind=PersistentVolumeClaim"

Name: "pvc-test", Namespace: "default"

Object: &{map["apiVersion":"v1" "kind":"PersistentVolumeClaim" "metadata":map["annotations":map["kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"PersistentVolumeClaim\",\"metadata\":{\"annotations\":{},\"name\":\"pvc-test\",\"namespace\":\"default\"},\"spec\":{\"accessModes\":[\"ReadWriteOnce\"],\"resources\":{\"requests\":{\"storage\":\"500Mi\"}}}}\n" "pv.kubernetes.io/bind-completed":"yes" "pv.kubernetes.io/bound-by-controller":"yes"] "creationTimestamp":"2019-12-24T10:46:05Z" "finalizers":["kubernetes.io/pvc-protection"] "name":"pvc-test" "namespace":"default" "resourceVersion":"15059" "selfLink":"/api/v1/namespaces/default/persistentvolumeclaims/pvc-test" "uid":"6a905af6-5e44-4940-ba87-e56f6e99df24"] "spec":map["accessModes":["ReadWriteOnce"] "resources":map["requests":map["storage":"500Mi"]] "volumeMode":"Filesystem" "volumeName":"my-pv02"] "status":map["accessModes":["ReadWriteOnce"] "capacity":map["storage":"500Mi"] "phase":"Bound"]]}

for: "pvc.yaml": persistentvolumeclaims "pvc-test" is forbidden: only dynamically provisioned pvc can be resized and the storageclass that provisions the pvc must support resize

我们发现报错了,错误信息如下:

persistentvolumeclaims "pvc-test" is forbidden: only dynamically provisioned pvc can be resized and the storageclass that provisions the pvc must support resize

它的意思就是说只有动态供应的pvc可以调整大小,供应pvc的存储类必须支持调整大小。也就是说我们手动创建PV,PVC模式是不支持调整大小的。

我们现在来验证一下用storageclass创建的PVC。
(1)、因为我们使用nfs作为后端存储,所以我们需要先创建一个nfs-client,YAML文件如下:

---

apiVersion: v1

kind: ServiceAccount

metadata:

  name: nfs-client-provisioner

---

apiVersion: rbac.authorization.k8s.io/v1

kind: ClusterRole

metadata:

  name: nfs-client-provisioner-clusterrole

rules:

  - apiGroups: [""]

    resources: ["persistentvolumes"]

    verbs: ["get", "list", "watch", "create", "delete"]

  - apiGroups: [""]

    resources: ["persistentvolumeclaims"]

    verbs: ["get", "list", "watch", "update"]

  - apiGroups: ["storage.k8s.io"]

    resources: ["storageclasses"]

    verbs: ["get", "list", "watch"]

  - apiGroups: [""]

    resources: ["events"]

    verbs: ["list", "watch", "create", "update", "patch"]

  - apiGroups: [""]

    resources: ["endpoints"]

    verbs: ["create", "delete", "get", "list", "watch", "patch", "update"]

---

apiVersion: rbac.authorization.k8s.io/v1

kind: ClusterRoleBinding

metadata:

  name: nfs-client-provisioner-clusterrolebinding

subjects:

- kind: ServiceAccount

  name: nfs-client-provisioner

  namespace: default

roleRef:

  kind: ClusterRole

  name: nfs-client-provisioner-clusterrole

  apiGroup: rbac.authorization.k8s.io

---

apiVersion: extensions/v1beta1

kind: Deployment

metadata:

  name: nfs-client-prosioner

spec:

  replicas: 1

  strategy:

    type: Recreate

  template:

    metadata:

      labels:

        app: nfs-client-prosioner

    spec:

      serviceAccountName: nfs-client-provisioner

      containers:

      - name: nfs-client-prosioner

        image: registry.cn-hangzhou.aliyuncs.com/rookieops/nfs-client-provisioner:v0.1

        imagePullPolicy: IfNotPresent

        volumeMounts:

        - name: nfs-client-root

          mountPath: /data/pv

        env:

        - name: PROVISIONER_NAME

          value: rookieops/nfs

        - name: NFS_SERVER

          value: 10.1.10.128

        - name: NFS_PATH

          value: /data/k8s

      volumes:

      - name: nfs-client-root

        nfs:

          server: 10.1.10.128

          path: /data/k8s

创建YAML文件

# kubectl apply -f !$

kubectl apply -f nfs-client.yaml

serviceaccount/nfs-client-provisioner created

clusterrole.rbac.authorization.k8s.io/nfs-client-provisioner-clusterrole created

clusterrolebinding.rbac.authorization.k8s.io/nfs-client-provisioner-clusterrolebinding created

deployment.extensions/nfs-client-prosioner created

# kubectl get pod

NAME                                    READY   STATUS    RESTARTS   AGE

nfs-client-prosioner-56f44c675b-t2ml9   1/1     Running   0          6s

(1)我们创建一个普通的StorageClass(storageclass.yaml)

apiVersion: storage.k8s.io/v1

kind: StorageClass

metadata:

  name: nfs-client-storageclass

provisioner: rookieops/nfs

创建这个YAML文件

# kubectl apply -f storageclass.yaml

storageclass.storage.k8s.io/nfs-client-storageclass created

# kubectl get storageclasses.storage.k8s.io

NAME                      PROVISIONER     AGE

nfs-client-storageclass   rookieops/nfs   34s

创建一个PVC(storageclass-pvc.yaml)

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: test-nfs-pvc2

  annotations:

    volume.beta.kubernetes.io/storage-class: "nfs-client-storageclass"

spec:

  accessModes:

    - ReadWriteMany

  resources:

    requests:

      storage: 1Mi

创建这个YAML文件

# kubectl apply -f storageclass-pvc.yaml

persistentvolumeclaim/test-nfs-pvc2 created

# kubectl get pvc

NAME            STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS              AGE

pvc-test        Bound    my-pv02                                    500Mi      RWO                                      26d

test-nfs-pvc2   Bound    pvc-9dd9c608-6875-4609-829c-c92920aaa783   1Mi        RWX            nfs-client-storageclass   21s

我们看到已经Bound了,我们现在直接修改pvc(storageclass-pvc.yaml)

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: test-nfs-pvc2

  annotations:

    volume.beta.kubernetes.io/storage-class: "nfs-client-storageclass"

spec:

  accessModes:

    - ReadWriteMany

  resources:

    requests:

      storage: 100Mi

然后我们执行这个YAML文件

# kubectl apply -f storageclass-pvc.yaml

Error from server (Forbidden): error when applying patch:

{"metadata":{"annotations":{"kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"PersistentVolumeClaim\",\"metadata\":{\"annotations\":{\"volume.beta.kubernetes.io/storage-class\":\"nfs-client-storageclass\"},\"name\":\"test-nfs-pvc2\",\"namespace\":\"default\"},\"spec\":{\"accessModes\":[\"ReadWriteMany\"],\"resources\":{\"requests\":{\"storage\":\"100Mi\"}}}}\n"}},"spec":{"resources":{"requests":{"storage":"100Mi"}}}}

to:

Resource: "/v1, Resource=persistentvolumeclaims", GroupVersionKind: "/v1, Kind=PersistentVolumeClaim"

Name: "test-nfs-pvc2", Namespace: "default"

Object: &{map["apiVersion":"v1" "kind":"PersistentVolumeClaim" "metadata":map["annotations":map["kubectl.kubernetes.io/last-applied-configuration":"{\"apiVersion\":\"v1\",\"kind\":\"PersistentVolumeClaim\",\"metadata\":{\"annotations\":{\"volume.beta.kubernetes.io/storage-class\":\"nfs-client-storageclass\"},\"name\":\"test-nfs-pvc2\",\"namespace\":\"default\"},\"spec\":{\"accessModes\":[\"ReadWriteMany\"],\"resources\":{\"requests\":{\"storage\":\"1Mi\"}}}}\n" "pv.kubernetes.io/bind-completed":"yes" "pv.kubernetes.io/bound-by-controller":"yes" "volume.beta.kubernetes.io/storage-class":"nfs-client-storageclass" "volume.beta.kubernetes.io/storage-provisioner":"rookieops/nfs"] "creationTimestamp":"2020-01-20T06:04:20Z" "finalizers":["kubernetes.io/pvc-protection"] "name":"test-nfs-pvc2" "namespace":"default" "resourceVersion":"29483" "selfLink":"/api/v1/namespaces/default/persistentvolumeclaims/test-nfs-pvc2" "uid":"9dd9c608-6875-4609-829c-c92920aaa783"] "spec":map["accessModes":["ReadWriteMany"] "resources":map["requests":map["storage":"1Mi"]] "volumeMode":"Filesystem" "volumeName":"pvc-9dd9c608-6875-4609-829c-c92920aaa783"] "status":map["accessModes":["ReadWriteMany"] "capacity":map["storage":"1Mi"] "phase":"Bound"]]}

for: "storageclass-pvc.yaml": persistentvolumeclaims "test-nfs-pvc2" is forbidden: only dynamically provisioned pvc can be resized and the storageclass that provisions the pvc must support resize

发现报与上面一样的错,这是因为要支持动态扩容需要满足两个条件:

我们由于是测试,申请的资源比较少,我们直接对StorageClass对象进行修改(storageclass.yaml),如下:

apiVersion: storage.k8s.io/v1

kind: StorageClass

metadata:

  name: nfs-client-storageclass

provisioner: rookieops/nfs

allowVolumeExpansion: true

然后我们重新申明一下

# kubectl apply -f storageclass.yaml

storageclass.storage.k8s.io/nfs-client-storageclass configured

我们再次创建前面的storageclass-pvc.yaml文件

# kubectl apply -f storageclass-pvc.yaml

persistentvolumeclaim/test-nfs-pvc2 configured

我们发现这次没有报错,我们查看一下这个PVC

# kubectl get pvc

NAME            STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS              AGE

pvc-test        Bound    my-pv02                                    500Mi      RWO                                      26d

test-nfs-pvc2   Bound    pvc-9dd9c608-6875-4609-829c-c92920aaa783   1Mi        RWX            nfs-client-storageclass   14m

我们一看,发现并没有扩展成功,这是为什么呢?我们describe一下这个pvc,发现如下提示:

# kubectl describe pvc test-nfs-pvc2

...

Warning  ExternalExpanding      7m43s  volume_expand

Ignoring the PVC: didn't find a plugin capable of expanding the volume; waiting for an external controller to process this PVC.

报错信息为:没有找到可扩展的插件。
我上官方网站一看,原来人家已经说的很清楚了:Although the feature is enabled by default, a cluster admin must opt-in to allow users to resize their volumes. Kubernetes v1.11 ships with volume expansion support for the following in-tree volume plugins: AWS-EBS, GCE-PD, Azure Disk, Azure File, Glusterfs, Cinder, Portworx, and Ceph RBD.

我们的NFS并不被支持(用NFS做后端存储的小伙伴注意了哈)。

标签:做后,kubernetes,storage,PVC,pvc,client,nfs,storageclass,test
来源: https://blog.51cto.com/15080014/2654326