k8s 存储原理、hostpath nfs-pvc

1、k8s 存储原理

底层存储支持各种方式，NAS、云盘、CEPH是我们常用的存储方式之一。
这是最底层的硬件存储，在底层硬件基础之上再开辟 PV(Persistent Volume)。
通过PV申请PVC(PersistentVolumeClaim)资源。
实现方式分为两种，通过定义PV再定义PVC; 直接动态申请PVC。

2、卷访问模式
1 ) RWO ROM RWM

ReadWriteOnce   卷可以被一个节点以读写方式挂载；
ReadOnlyMany     卷可以被多个节点以只读方式挂载；
ReadWriteMany   卷可以被多个节点以读写方式挂载。

2)pv 的几种生命周期

3) pv生命周期的4阶段

Available      可用状态，未与PVC绑定
Bound           绑定状态
Released      绑定的PVC删除、资源释放、未被集群收回
Failed           资源回收失败

3、kubernetes目录挂载方式

0 ) emptyDir

emptyDir，它的生命周期和所属的 Pod 是相同的，同生共死。
empty Volume 在 Pod 分配到 Node 上时会被创建,  自动分配一个目录。
当 Pod 从 Node 上删除或者迁移时，emptyDir 中的数据会被永久删除

1）hostpath模式，创建在node节点，与pod 生命周期不同
将nginx 镜像中/data 挂载到 宿中的/datak8s, yaml文件如下:

apiVersion: v1
kind: Pod
metadata:
  name: test-pd-hostpath
spec:
  containers:
  - image: nginx:1.14.2
    name: test-container
    volumeMounts:
    - mountPath: /data/
      name: test-volume
  volumes:
  - name: test-volume
    hostPath:
      path: /datak8s
      type: DirectoryOrCreate

hostPath type 模式如下:

在node节点 /datak8s 下创建文件

删除test-pd-hostpath,修改yaml文件

kubectl apply -f hostpath.yaml

查看镜像内目录

在低版本某云中,使用该种对应关系进行日志收集, node节点使用同样的目录,pod中由程序 logback 来创建日志

2、使用nfs-pvc 做为数据存储 或者在云端可以使用云存储挂载但仅局限于RWO环境

k8s 挂载NFS的 rbac.yaml 创建

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
  namespace: default
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    namespace: default
roleRef:
  kind: Role
  name: leader-locking-nfs-client-provisioner
  apiGroup: rbac.authorization.k8s.io

#pvc 创建

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-test
spec:
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Recycle
  nfs:
    path: /nfs/k8s
    server: 10.0.0.181
---
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: pvc-test
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 100Mi

#创建yaml文件并挂载pvc

vim nginx2-pvc-deployment.yaml 

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx2-deployment
  labels:
    app: nginx2
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx2
  template:
    metadata:
      labels:
        app: nginx2
    spec:
      containers:
      - name: nginx2
        image: nginx:1.14.2
        command: [ "sh", "-c", "while [ true ]; do echo 'Hello'; sleep 10; done | tee -a /logs/hello.txt" ]
        ports:
        - containerPort: 80
        volumeMounts:
        - name: nginx2-pvc-storageclass
          mountPath: /logs
      volumes:
      - name: nginx2-pvc-storageclass
        persistentVolumeClaim:
          claimName: pvc-test

#部署nginx2 deployment

kubectl apply -f nginx2-pvc-deployment.yaml

#删除 nginx2，hello.txt 文件还存在

[root@k8s01 storage]# kubectl delete -f nginx2-pvc-deployment.yaml 
deployment.apps "nginx2-deployment" deleted