PersistentVolume、PersistentVolumeClaim

概念

PersistentVolume （PV）
是由管理员设置的存储，它是群集的一部分。就像节点是集群中的资源一样，PV 也是集群中的资源。 PV 是
Volume 之类的卷插件，但具有独立于使用 PV 的 Pod 的生命周期。此 API 对象包含存储实现的细节，即 NFS、
iSCSI 或特定于云供应商的存储系统

PersistentVolumeClaim （PVC）
是用户存储的请求。它与 Pod 相似。Pod 消耗节点资源，PVC 消耗 PV 资源。Pod 可以请求特定级别的资源
（CPU 和内存）。声明可以请求特定的大小和访问模式（例如，可以以读/写一次或 只读多次模式挂载）

绑定

每个pod都有自己的请求模板，创建对应pvc,pvc通过storageClassName、accessModes参数与pv进行匹配，匹配成功后与之绑定。一旦 PV 和 PVC 绑定后， PersistentVolumeClaim 绑定是排他性的，不管它们是如何绑定的。 Pod、PVC 跟PV 绑定是一对一的映射

访问模式（accessModes）

• ReadWriteOnce——该卷可以被单个节点以读/写模式挂载

• ReadOnlyMany——该卷可以被多个节点以只读模式挂载

• ReadWriteMany——该卷可以被多个节点以读/写模式挂载

  在命令行中，访问模式缩写为：

  ​ RWO - ReadWriteOnce
  ​ ROX - ReadOnlyMany
  ​ RWX - ReadWriteMany

回收策略

• Retain（保留）——手动回收
• Delete（删除）——关联的存储资产（例如 AWS EBS、GCE PD、Azure Disk 和 OpenStack Cinder 卷）
  将被删除

状态

• 卷可以处于以下的某种状态：
• Available（可用）——一块空闲资源还没有被任何声明绑定
• Bound（已绑定）——卷已经被声明绑定
• Released（已释放）——声明被删除，但是资源还未被集群重新声明
• Failed（失败）——该卷的自动回收失败

演示说明

kubernetes使用存储有两种方式：静态与动态
静态:需管理员手动编写pv.yaml并创建pv路径
动态:通过pvc请求动态创建pv同时动态pv路径

静态

创建

local-storageClass.yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-storage
#表示不需要自动创建PV
provisioner: kubernetes.io/no-provisioner  
#WaitForFirstConsumer表示需要等到Pod运行之后才让PVC和PV绑定。因为在使用Local Persistent Volume的时候PV和对应的PVC必须
#要跟随Pod在同一node下面，否则会调度失败。
volumeBindingMode: WaitForFirstConsumer   
parameters:
#删除时是否存档，false表示不存档，即删除数据，true表示存档，即重命名路径,默认为true
#命名格式为oldPath前面增加archived-的前缀
  archiveOnDelete: "true"
#回收策略是手动回收
reclaimPolicy: Retain
#允许扩容
allowVolumeExpansion: true

创建pvc static-pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: static-pvc
spec:
  selector:
    matchLabels:
      app: static-pv
  accessModes:
    - ReadWriteOnce
  #这边的storageClassName要与static-pv.yaml匹配，同时selector标签匹配时，才能够与pv进行绑定
  storageClassName: local-storage
  resources:
    requests:
      storage: 1Gi

[root@master pv]# kubectl get pvc
NAME         STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS    AGE
static-pvc   Pending                                      local-storage   3s
#由于local-storageClass.yaml使用的是WaitForFirstConsumer.pod还没有进行调用，所有pvc处于挂起状态

创建pv static-pv.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: static-pv
  labels:
    app: static-pv
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  #与local-storageClass.yaml中name标签相同，否则不需要等待pod调用，pv创建之后就可以直接bound
  storageClassName: local-storage
  #local字段指定了它是一个 Local Persistent Volume，而path 字段，指定的这个 PV 对应的本地磁盘的路径:/static
  #并且用nodeAffinity指定这个PV必须运行在node1节点上
  local:
    path: /static
  nodeAffinity:
    required:
      nodeSelectorTerms:
        - matchExpressions:
            - key: kubernetes.io/hostname
              operator: In
              values:
                - node1

$ kubectl apply -f static-pv.yaml 
persistentvolume/static-pv created
$ kubectl get pv
NAME        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS    REASON   AGE
static-pv   1Gi        RWO            Retain           Available           local-storage            3s

创建pod

apiVersion: v1
kind: Pod
metadata:
  name: static-pod
spec:
  containers:
    - image: mynginx:v1
      name: mynginx
      command:
        - "/bin/sh"
      args:
        - "-c"
        - "echo 'hello k8s local storage' > /mnt/SUCCESS && sleep 36000 || exit 1"
      volumeMounts:
        - mountPath: /mnt
          name: example-volume
  volumes:
    - name: example-volume
      persistentVolumeClaim:
    #与static-pvc.yaml中metadata-name名称一致，表示pod调用该pvc
        claimName: static-pvc  

此时发现pod一直处于ContainerCreating状态，kubectl dsrcribe查看提示/static，与static-pv.yaml文件中path字段对应。原来master节点根目录下没有static文件夹。

$ kubectl describe pod static-pod
...
  Warning  FailedMount  8s (x5 over 15s)  kubelet, master    MountVolume.NewMounter initialization failed for volume "static-pv" : path "/static" does not exist

创建该文件夹后，pod运行 pvc

$ kubectl get pod
NAME         READY   STATUS    RESTARTS   AGE
static-pod   1/1     Running   0          4m37s

$ kubectl get pvc
NAME         STATUS   VOLUME      CAPACITY   ACCESS MODES   STORAGECLASS    AGE
static-pvc   Bound    static-pv   1Gi        RWO            local-storage   6m10s

$ kubectl get pv
NAME        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                STORAGECLASS    REASON   AGE
static-pv   1Gi        RWO            Retain           Bound    default/static-pvc   local-storage            13m

$ cat /static/SUCCESS 
hello k8s local storage

回收

由于回收策略是手动回收，所以当pod和pvc被删除时、本地存储的数据不会被删除，pv会变成Released（释放状态）

$ kubectl get pv
NAME        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS     CLAIM                STORAGECLASS    REASON   AGE
static-pv   1Gi        RWO            Retain           Released   default/static-pvc   local-storage            3m45s

$ ls /static/SUCCESS 
/static/SUCCESS

pv会变成Released（释放状态）无法在被绑定，原因是pv中依然留存着曾经的绑定记录

$ kubectl get pv static-pv -o yaml
...
  claimRef:
    apiVersion: v1
    kind: PersistentVolumeClaim
    name: static-pvc
    namespace: default
    resourceVersion: "41242"
    uid: f49e6358-1c09-4cb1-b594-1f279747359f
...

$ kubectl edit pv static-pv
#删除上面的claimRef后，恢复成Available（可用）状态
$ kubectl get pv
NAME        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS      CLAIM   STORAGECLASS    REASON   AGE
static-pv   1Gi        RWO            Retain           Available           local-storage            9m7s

动态

创建

服务器类型	ip
master	192.168.234.132
node1	192.168.234.134
nfs共享存储	192.168.234.133

本地存储local-path-provisioner

local-path-provisioner.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: local-path-storage

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: local-path-provisioner-service-account
  namespace: local-path-storage

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: local-path-provisioner-role
rules:
  - apiGroups: [ "" ]
    resources: [ "nodes", "persistentvolumeclaims", "configmaps" ]
    verbs: [ "get", "list", "watch" ]
  - apiGroups: [ "" ]
    resources: [ "endpoints", "persistentvolumes", "pods" ]
    verbs: [ "*" ]
  - apiGroups: [ "" ]
    resources: [ "events" ]
    verbs: [ "create", "patch" ]
  - apiGroups: [ "storage.k8s.io" ]
    resources: [ "storageclasses" ]
    verbs: [ "get", "list", "watch" ]

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: local-path-provisioner-bind
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: local-path-provisioner-role
subjects:
  - kind: ServiceAccount
    name: local-path-provisioner-service-account
    namespace: local-path-storage

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: local-path-provisioner
  namespace: local-path-storage
spec:
  replicas: 1
  selector:
    matchLabels:
      app: local-path-provisioner
  template:
    metadata:
      labels:
        app: local-path-provisioner
    spec:
      serviceAccountName: local-path-provisioner-service-account
      containers:
        - name: local-path-provisioner
          image: rancher/local-path-provisioner:v0.0.22
          imagePullPolicy: IfNotPresent
          command:
            - local-path-provisioner
            - --debug
            - start
            - --config
            - /etc/config/config.json
          volumeMounts:
            - name: config-volume
              mountPath: /etc/config/
          env:
            - name: POD_NAMESPACE
              valueFrom:
                fieldRef:
                  fieldPath: metadata.namespace
      volumes:
        - name: config-volume
          configMap:
            name: local-path-config

---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-path
provisioner: rancher.io/local-path
volumeBindingMode: WaitForFirstConsumer
reclaimPolicy: Delete

---
kind: ConfigMap
apiVersion: v1
metadata:
  name: local-path-config
  namespace: local-path-storage
data:
  config.json: |-
    {
            "nodePathMap":[
            {
                    "node":"DEFAULT_PATH_FOR_NON_LISTED_NODES",
                    "paths":["/opt/local-path-provisioner"]
            }
            ]
    }
  setup: |-
    #!/bin/sh
    set -eu
    mkdir -m 0777 -p "$VOL_DIR"
  teardown: |-
    #!/bin/sh
    set -eu
    rm -rf "$VOL_DIR"
  helperPod.yaml: |-
    apiVersion: v1
    kind: Pod
    metadata:
      name: helper-pod
    spec:
      containers:
      - name: helper-pod
        image: busybox
        imagePullPolicy: IfNotPresent

默认创建在/opt/local-path-provisioner目录下,如果生产最大目录不是opt下需要修改，创建规则:pv-namespace-pvc
调用的pvc

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: local-pvc
spec:
  accessModes:
    - ReadWriteOnce     #在rancher/local-path-provisioner里，这里不能用ReadWriteMany
  storageClassName: local-path #与local-path-provisioner.yaml  StorageClass name一致
  resources:
    requests:
      storage: 50Gi

nfs共享存储:

$ yum -y install nfs-utils
#启动rpcbind、nfs服务
$ systemctl restart rpcbind && systemctl enable rpcbind
$ systemctl restart nfs && systemctl enable nfs
$ cat /etc/exports
/opt  192.168.234.132(insecure,rw,sync,no_root_squash)
#配置生效
$ exportfs -r
#查看生效
$ exportfs
/opt            192.168.234.132

master：

#目的是能够使用showmount命令
$ yum -y install nfs-utils  
#出现以下输出，即表示nfs可正常挂载
$ showmount -e 192.168.234.133
Export list for 192.168.234.133:
/opt 192.168.234.132

NFS Provisioner 是一个自动配置卷程序，它使用现有的和已配置的 NFS 服务器来支持通过持久卷声明动态配置 Kubernetes 持久卷。
Kubernetes 集群大部分是基于 RBAC 的权限控制，所以创建一个一定权限的 ServiceAccount 与后面要创建的 “NFS Provisioner” 绑定 nfs-rbac.yaml
nfs-rbac.yaml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: nfs-client-provisioner
  namespace: default
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: nfs-client-provisioner-runner
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: ["create", "update", "patch"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: run-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    namespace: default
roleRef:
  kind: ClusterRole
  name: nfs-client-provisioner-runner
  apiGroup: rbac.authorization.k8s.io
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
  namespace: default
rules:
  - apiGroups: [""]
    resources: ["endpoints"]
    verbs: ["get", "list", "watch", "create", "update", "patch"]
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    namespace: default
roleRef:
  kind: Role
  name: leader-locking-nfs-client-provisioner
  apiGroup: rbac.authorization.k8s.io

nfs-storageClass.yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: share-storage
  annotations:
    storageclass.kubernetes.io/is-default-class: "true" #将nfs设置成默认存储类
provisioner: nfs-client #这里的值要和nfs-provisioner文件中PROVISIONER_NAME的值保持一致 
parameters:
  #pathPattern: "${.PVC.namespace}-${.PVC.name}"  #可以指定在nfs机器上产生的文件夹名称，默认是namespace−{pvcName}-${pvName}
  archiveOnDelete: "true"  #删除pv的时候，pv的内容是否要备份
reclaimPolicy: Retain      #回收策略-手动回收
allowVolumeExpansion: true #允许扩容

nfs-provisioner.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nfs-client-provisioner  
  labels:
    app: nfs-client-provisioner
  namespace: default
spec:
  replicas: 1
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: nfs-client-provisioner  
  template:
    metadata:
      labels:
        app: nfs-client-provisioner
    spec:
      serviceAccountName: nfs-client-provisioner #与nfs-rbac.yaml文件中一致
      containers:
        - name: nfs-client-provisioner
          image: quay.io/external_storage/nfs-client-provisioner:latest
          volumeMounts:
            - name: nfs-client-root
              mountPath: /persistentvolumes
          env:
            - name: PROVISIONER_NAME
              value: nfs-client     #与nfs-storageClass.yaml中保持一致
            - name: NFS_SERVER
              value: 192.168.234.133 #真实nfs服务端ip
            - name: NFS_PATH
              value: /opt            #挂载的目录
      volumes:
        - name: nfs-client-root
          nfs:
            server: 192.168.234.133  #真实nfs服务端ip
            path: /opt               #挂载的目录

$ kubectl apply -f nfs-storageClass.yaml
$ kubectl apply -f nfs-rbac.yaml
$ kubectl apply -f nfs-provisioner.yaml
$ kubectl get deployment
NAME                     READY   UP-TO-DATE   AVAILABLE   AGE
nfs-client-provisioner   1/1     1            1           11m
$ kubectl get pod
NAME                                      READY   STATUS    RESTARTS   AGE
nfs-client-provisioner-75bc8db759-bhz56   1/1     Running   0          8m51s

#此时并没有pv、pvc服务
$ kubectl get pv
No resources found in default namespace.
$ kubectl get pvc
No resources found in default namespace.

创建pvc nfs-pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-pvc
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: share-storage  #与nfs-storageClass.yaml文件中name一致
  resources:
    requests:
      storage: 2Gi

$ kubectl apply -f nfs-pvc.yaml

$ kubectl get pvc
NAME      STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS    AGE
nfs-pvc   Bound    pvc-f990a82a-14a0-4292-aeb3-9f34a68f01be   2Gi        RWO            share-storage   107s

$ kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM             STORAGECLASS    REASON   AGE
pvc-f990a82a-14a0-4292-aeb3-9f34a68f01be   2Gi        RWO            Retain           Bound    default/nfs-pvc   share-storage            109s

我们发现，与静态不同我们不需要手动的创建pv，pvc请求自动创建pv，于此同时在服务端(192.168.234.133)服务器的/opt目录下，已经创建了文件夹 名称格式为:namespace−{pvcName}-${pvName}。

$ pwd
ll /opt/default-nfs-pvc-pvc-f990a82a-14a0-4292-aeb3-9f34a68f01be

创建pod nfs-pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nfs-pod
spec:
  nodeName: master
  containers:
    - image: mynginx:v1
      name: mynginx
      command:
        - "/bin/sh"
      args:
        - "-c"
        - "echo 'hello k8s local storage' > /mnt/SUCCESS && sleep 36000 || exit 1"
      volumeMounts:
        - mountPath: /mnt
          name: example-volume
  volumes:
    - name: example-volume
      persistentVolumeClaim:
        claimName: nfs-pvc

$ kubectl apply -f nfs-pod.yaml

服务端：
$ ls default-nfs-pvc-pvc-0e543a5b-e9df-46ab-b778-f769f96f6ea4/SUCCESS 
default-nfs-pvc-pvc-0e543a5b-e9df-46ab-b778-f769f96f6ea4/SUCCESS

回收

回收与静态相似。由于回收策略是手动回收，所以当pod和pvc被删除时、本地存储的数据不会被删除，pv会变成Released（释放状态）该状态下同样无法被绑定，如果再次创建pvc时，会生成新的pv，与静态相同，只有将claimRef删除后，恢复成Available（可用）状态

#pod与pvc删除后，pv会变成Released状态
$ kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS     CLAIM             STORAGECLASS    REASON   AGE
pvc-f990a82a-14a0-4292-aeb3-9f34a68f01be   2Gi        RWO            Retain           Released   default/nfs-pvc   share-storage            4h25m
#nfs服务端
$ ls default-nfs-pvc-pvc-f990a82a-14a0-4292-aeb3-9f34a68f01be
SUCCESS

#再次创建pvc
$ kubectl apply -f nfs-pvc.yaml

$ kubectl get pvc
NAME      STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS    AGE
nfs-pvc   Bound    pvc-97c8bca2-be92-49f6-9d76-126c7e8c4479   2Gi        RWO            share-storage   6s
#原先的pvc是Released无法被重新绑定，会生成新的pv
$ kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS     CLAIM             STORAGECLASS    REASON   AGE
pvc-97c8bca2-be92-49f6-9d76-126c7e8c4479   2Gi        RWO            Retain           Bound      default/nfs-pvc   share-storage            4s
pvc-f990a82a-14a0-4292-aeb3-9f34a68f01be   2Gi        RWO            Retain           Released   default/nfs-pvc   share-storage            62m

#nfs服务端
$ ll
总用量 0
drwxrwxrwx. 3 root root 18 3月  15 17:31 default-nfs-pvc-pvc-97c8bca2-be92-49f6-9d76-126c7e8c4479
drwxrwxrwx. 2 root root  6 3月  15 21:58 default-nfs-pvc-pvc-f990a82a-14a0-4292-aeb3-9f34a68f01be