1. Types of data persistence:
1.emptyDir: Can only be used as temporary storage.If the container is deleted, the data still exists, and if the Pod is deleted, the data is deleted.
2.HostPath: Less scenarios increase the coupling between Pod and nodes.
3.PV, PVC: based on NFS services.The PV state must be Available, the access mode must be the same, and the name of the storage class must be the same.
Error: Pod keeps restarting:
1. The swap was not shut down, causing the cluster to malfunction.
2. Insufficient memory will cause the running service to restart.
Note: Create PV based on NFs, with PVC.
And you need to create the host directory needed for the PV.
2. Make an experimental analogy, if there are two PVs with different space sizes in the cluster, how PVC relates to PV. 1. Create a PV (create two PVs of different space sizes, web-pv 1 and web-pv2) 1.[root@master yaml]# vim web1.yaml 2. 3.kind: PersistentVolume 4.apiVersion: v1 5.metadata: 6. name: web-pv1 7.spec: 8. accessModes: 9. - ReadWriteOnce 10. capacity: 11. storage: 1Gi 12. persistentVolumeReclaimPolicy: Recycle 13. storageClassName: nfs 14. nfs: 15. path: /nfsdata/web1 16. server: 192.168.1.1 17. 18.[root@master yaml]# mkdir /nfsdata/web1 19.[root@master yaml]# kubectl apply -f web1.yaml 20.persistentvolume/web-pv1 created 21.[root@master yaml]# kubectl get pv 22.NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE 23.web-pv1 1Gi RWO Recycle Available nfs 7s
2.Create a second Pv 1.[root@master yaml]# vim web2.yaml 2.kind: PersistentVolume 3.apiVersion: v1 4.metadata: 5. name: web-pv2 6.spec: 7. accessModes: 8. - ReadWriteOnce 9. capacity: 10. storage: 2Gi 11. persistentVolumeReclaimPolicy: Recycle 12. storageClassName: nfs 13. nfs: 14. path: /nfsdata/web2 15. server: 192.168.1.1 16. 17.[root@master yaml]# kubectl apply -f web2.yaml 18.persistentvolume/web-pv2 created 19. 20.[root@master yaml]# kubectl get pv 21.NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE 22.web-pv1 1Gi RWO Recycle Available nfs 103s 23.web-pv2 2Gi RWO Recycle Available nfs 14s
3. Create PVC br/>1.[root@master yaml]# vim web-pvc.yaml
2.kind: PersistentVolumeClaim br/>3.apiVersion: v1
4.metadata:
5. name: web-pvc
6.spec:
7. accessModes:
8. - ReadWriteOnce
9. resources:
10. requests:
11. storage: 1Gi
12. storageClassName: nfs
13.[root@master yaml]# kubectl apply -f web-pvc.yaml
14.persistentvolumeclaim/web-pvc created br/>15.[root@master yaml]# kubectl get pvc
16.NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE br/>17.web-pvc Bound web-pv1 1Gi RWO nfs 5s
18.[root@master yaml]# kubectl get pv
19.NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
20.web-pv1 1Gi RWO Recycle Bound default/web-pvc nfs 8m59s
21.web-pv2 2Gi RWO Recycle Available nfs 7m30s
From the above experiment:
If there are many similar PVs in K8s cluster, PVC will not only consider name and access control mode, but also the size of PVC application space and allocate the most suitable size of PV when requesting space from PV.
3. Analyse the function and advantages of storageclass resource object.
1. Data persistence can be achieved by using PV and PVC. If our PV capacity is 10G, access mode is defined as RWO, and the storage space of our PVC application is 5G, the requested PV capacity will be wasted because access mode can only be mounted by a single node.Also, it is cumbersome for us to create PVs every time, so there is a Storage Class needed for dynamic and automatic creation.
Storage Class: Storage Class is a kind of K8s resource type. It is a logical group that administrators create to manage PV more easily. It can be classified according to the performance of storage system, or integrated quality of service, backup policy and so on.But k8s does not know what the category is, it is used as a description.
Advantages: Dynamic PV creation is supported. When users use persistent storage, they do not need to create PV in advance, but directly create PVC. It is very convenient.
The name of the storage class object is important, and in addition to the name, there are three key fields:
Provisioner: A storage system that provides storage resources.k8s has built-in multiple providers whose names are prefixed with "kubernetes.io".It can also be customized.
Parameters: Storage classes use parameters to describe the volume to which they are associated, noting that different supplier parameters vary.
ReclaimPlicy:The recycling strategy for PV.
More about Storage Class:
https://www.kubernetes.org.cn/pvpvcstorageclass
2. Do an experiment to create a PV automatically:
Run a web service based on nginx, using the Deployment resource object, replicas=3. Persist the storage directory as the default home directory, and use the storage class to automatically create the PV.
Based on NFS:
1)First NFS Opening of services: 1.[root@master yaml]# yum install -y nfs-utils rpcbind #Note here that all three install NFS services. 2.[root@master yaml]# vim /etc/exports 3./nfsdata *(rw,sync,no_root_squash) 4.[root@master yaml]# mkdir /nfsdata 5.[root@master yaml]# systemctl start rpcbind 6.[root@master yaml]# systemctl start nfs-server.service 7.[root@master yaml]# showmount -e 8.Export list for master: 9./nfsdata *
2)Establish RBAC To grant authorization: 1.[root@master yaml]# vim rbac-rolebind.yaml #To give SC resources permission to operate on the K8s cluster.* 2. 3.kind: Namespace 4.apiVersion: v1 5.metadata: 6. name: lbs-test 7.--- 8.apiVersion: v1 9.kind: ServiceAccount #Create an Rbac authorized user.And define permissions.* 10.metadata: 11. name: nfs-provisioner 12. namespace: lbs-test 13.--- 14.apiVersion: rbac.authorization.k8s.io/v1 15.kind: ClusterRole 16.metadata: 17. name: nfs-provisioner-runner 18. namespace: lbs-test 19.rules: 20. - apiGroups: [""] 21. resources: ["persistentvolumes"] 22. verbs: ["get", "list", "watch", "create", "delete"] 23. - apiGroups: [""] 24. resources: ["persistentvolumeclaims"] 25. verbs: ["get", "list", "watch", "update"] 26. - apiGroups: ["storage.k8s.io"] 27. resources: ["storageclasses"] 28. verbs: ["get", "list", "watch"] 29. - apiGroups: [""] 30. resources: ["events"] 31. verbs: ["watch", "create", "update", "patch"] 32. - apiGroups: [""] 33. resources: ["services", "endpoints"] 34. verbs: ["get","create","list", "watch","update"] 35. - apiGroups: ["extensions"] 36. resources: ["podsecuritypolicies"] 37. resourceNames: ["nfs-provisioner"] 38. verbs: ["use"] 39.--- 40.kind: ClusterRoleBinding 41.apiVersion: rbac.authorization.k8s.io/v1 42.metadata: 43. name: run-nfs-provisioner 44.subjects: 45. - kind: ServiceAccount 46. name: nfs-provisioner 47. namespace: lbs-test 48.roleRef: 49. kind: ClusterRole 50. name: nfs-provisioner-runner 51. apiGroup: rbac.authorization.k8s.io
Execute yaml file:
1.[root@master yaml]# kubectl apply -f rbac-rolebind.yaml namespace/lbh-test created serviceaccount/nfs-provisioner created clusterrole.rbac.authorization.k8s.io/nfs-provisioner-runner created clusterrolebinding.rbac.authorization.k8s.io/run-nfs-provisioner created
3)Establish nfs-client-provisioner Container: 1.[root@master yaml]# vim nfs-deployment.yaml 2. 3.apiVersion: extensions/v1beta1 4.kind: Deployment 5.metadata: 6. name: nfs-client-provisioner 7. namespace: lbs-test 8.spec: 9. replicas: 1 #Number of copies is 1 10. strategy: 11. type: Recreate 12. template: 13. metadata: 14. labels: 15. app: nfs-client-provisioner 16. spec: 17. serviceAccount: nfs-provisioner #Specify Account 18. containers: 19. - name: nfs-client-provisioner 20. image: registry.cn-hangzhou.aliyuncs.com/open-ali/nfs-client-provisioner #The mirror used.* 21. volumeMounts: 22. - name: nfs-client-root 23. mountPath: /persistentvolumes #Specify the mount directory within the container 24. env: 25. - name: PROVISIONER_NAME #This is the built-in variable for this container. 26. value: lbs-test #This is the value (name) of the variable above. 27. - name: NFS_SERVER #Built-in variable to specify the IP of the nfs service 28. value: 192.168.2.50 29. - name: NFS_PATH #Built-in variable, specified as nfs shared directory 30. value: /nfsdata 31. volumes: #Here is the path and IP of the nfs mounted above the container. 32. - name: nfs-client-root 33. nfs: 34. server: 192.168.2.50 35. path: /nfsdata
NFS-deployment:
What it does: It's actually an NFS client.It mounts remote NFS servers to the local directory through K8S's built-in NFS driver; it then associates itself as a storage provider with the storage class.
Execute yaml file: br/>1.[root@master yaml]# kubectl apply -f nfs-deployment.yaml
deployment.extensions/nfs-client-provisioner created
4)Establish SC(Storage Class)Automatic Creation pv 1.[root@master yaml]# vim test-storageclass.yaml 2.apiVersion: storage.k8s.io/v1 3.kind: StorageClass 4.metadata: 5. name: sc-nfs 6. namespace: lbs-test #Namespace 7.provisioner: lbs-test #This corresponds to the value in the env environment variable for deployment.* 8.reclaimPolicy: Retain #The recycling strategy is retain.* //Execute yaml file: 1.[root@master yaml]# kubectl apply -f test-storageclass.yaml storageclass.storage.k8s.io/sc-nfs created
5)Establish PVC 1.[root@master yaml]# vim test-pvc.yaml 2. 3.apiVersion: v1 4.kind: PersistentVolumeClaim 5.metadata: 6. name: lbs-claim 7. namespace: lbs-test 8. 9.spec: 10. storageClassName: sc-nfs Need to be associated with storageclass The same name 11. accessModes: 12. - ReadWriteMany 13. resources: 14. requests: 15. storage: 500Mi
When we finish creating PVC After that, one will be created automatically PV，Its purpose is to NFS Under the shared directory: 1.[root@master yaml]# ls /nfsdata/ lbs-test-lbs-claim-pvc-71262c5a-f866-4bc6-a22f-cd49daf13edf 2.[root@master yaml]# kubectl get pv -n lbs-test 3.NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE pvc-71262c5a-f866-4bc6-a22f-cd49daf13edf 500Mi RWX Delete Bound lbs-test/lbs-claim sc-nfs 26m
6)** Run the web service based on nginx, using Deployment resource objects, three copies, and the persistent storage directory as the default home directory.Change the contents of the default home directory to your own name, and verify that there is data in the PV directory where the data is automatically created.** Create Deployment Resource: 1.[root@master yaml]# vim nginx.yaml 2. 3.apiVersion: extensions/v1beta1 4.kind: Deployment 5.metadata: 6. name: lbs-web 7. namespace: lbs-test 8.spec: 9. replicas: 3 10. template: 11. metadata: 12. labels: 13. app: web 14. spec: 15. containers: 16. - name: nginx 17. image: nginx 18. volumeMounts: 19. - name: lbs-web 20. mountPath: /usr/share/nginx/html/ 21. volumes: 22. - name: lbs-web 23. persistentVolumeClaim: 24. claimName: lbs-claim
Execute the yaml file and view the Pod: 1.[root@master yaml]# kubectl apply -f nginx.yaml 2.deployment.extensions/lbh-web created 3. 4.[root@master yaml]# kubectl get pod -n lbs-test 5.NAME READY STATUS RESTARTS AGE 6.lbs-web-6d596b6666-68wls 1/1 Running 0 2m29s 7.lbs-web-6d596b6666-k8vz2 1/1 Running 0 2m29s 8.lbs-web-6d596b6666-pvppq 1/1 Running 0 2m29s
Enter containers to configure the page root directory: 1.[root@master yaml]# kubectl exec -it -n lbs-test lbs-web-6d596b6666-68wls /bin/bash 2.root@lbs-web-6d596b6666-68wls:/# cd /usr/share/nginx/html/ 3.root@lbs-web-6d596b6666-68wls:/usr/share/nginx/html# echo 123 > index.html 4.root@lbs-web-6d596b6666-68wls:/usr/share/nginx/html# ls 5.index.html 6.root@lbs-web-6d596b6666-68wls:/usr/share/nginx/html# exit
The other two steps are the same.
Check if there is data in the Auto-Create Score PV directory: 1.[root@master yaml]# cat /nfsdata/lbs-test-lbs-claim-pvc-71262c5a-f866-4bc6-a22f-cd49daf13edf/index.html 2.123
Access Web Test: 1.[root@master yaml]# kubectl get pod -o wide -n lbs-test 2.NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES 3.lbs-web-6d596b6666-68wls 1/1 Running 0 11m 10.244.2.7 node02 <none> <none> 4.lbs-web-6d596b6666-k8vz2 1/1 Running 0 11m 10.244.2.9 node02 <none> <none> 5.lbs-web-6d596b6666-pvppq 1/1 Running 0 11m 10.244.2.8 node02 <none> <none> 6.[root@master yaml]# curl 10.244.2.7 7.123
The page root directory in the nginx container is associated with the local nfs shared directory.
Data will not be lost because the container, pod, is deleted.