4.9、PVC扩容测试（Glusterfs）

我们前面已经介绍过静态PV是没办法进行扩容的，而且我们在用NFS做持久化存储的时候了解到要用动态PV并做扩容操作需要Kubernetes底层支持的存储，这次我们就用Glusterfs做扩容测试。

需要准备好Glusterfs，搭建地址为：

（1）、创建namespace，以下测试都在这个namespace下

# kubectl create ns rookieops
namespace/rookieops created

（1）、创建Secret（glusterfs-secret.yaml）

apiVersion: v1
kind: Secret
metadata:
  name: glusterfs-secret
  namespace: rookieops
data:
  key: YWRtaW5AUEBzc1cwcmQ=
type: kubernetes.io/glusterfs

创建secret对象

# kubectl apply -f glusterfs-secret.yaml 
secret/glusterfs-secret created
# kubectl get secret -n rookieops 
NAME                  TYPE                                  DATA   AGE
default-token-s7d65   kubernetes.io/service-account-token   3      2m26s
glusterfs-secret      kubernetes.io/glusterfs               1      5s

（2）、创建StorageClass（glusterfs-storageclass.yaml）

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: glusterfs-storageclass
  namespace: rookieops
parameters:
  resturl: "http://10.1.10.128:48080"
  clusterid: "cca360f44db482f03297a151886eea19"
  restauthenabled: "true"             #若heketi开启认证此处也必须开启auth认证
  restuser: "admin"
  secretName: "glusterfs-secret"      #name/namespace与secret资源中定义一致
  secretNamespace: "rookieops"
  volumetype: "replicate:3"
provisioner: kubernetes.io/glusterfs
reclaimPolicy: Delete
allowVolumeExpansion: true

创建storageclass对象

# kubectl apply -f  glusterfs-storageclass.yaml 
storageclass.storage.k8s.io/glusterfs-storageclass created
# kubectl get sc -n rookieops 
NAME                     PROVISIONER               RECLAIMPOLICY   VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION   AGE
glusterfs-storageclass   kubernetes.io/glusterfs   Delete          Immediate           false                  9s

（3）、创建PVC（glusterfs-pvc.yaml）

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: glusterfs-pvc
  namespace: rookieops
  annotations:
    volume.beta.kubernetes.io/storage-class: glusterfs-storageclass
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

创建PVC对象

# kubectl apply -f  glusterfs-pvc.yaml 
persistentvolumeclaim/glusterfs-pvc created
# kubectl get pvc -n rookieops 
NAME            STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS             AGE
glusterfs-pvc   Bound    pvc-cfae01a0-cb37-4fcc-8640-8ef604ae3874   1Gi        RWO            glusterfs-storageclass   46s

（4）、然后我们对其进行扩容，直接在PVC的YAML文件中修改其大小

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: glusterfs-pvc
  namespace: rookieops
  annotations:
    volume.beta.kubernetes.io/storage-class: glusterfs-storageclass
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 2Gi

然后更新PVC对象

# kubectl apply -f  glusterfs-pvc.yaml 
# kubectl get pvc -n rookieops 
NAME            STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS             AGE
glusterfs-pvc   Bound    pvc-29c667db-b103-49f8-9b2f-87ca5d29f751   2Gi        RWO            glusterfs-storageclass   71s

我们describe以下PVC

Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      2Gi
Access Modes:  RWO
VolumeMode:    Filesystem
Mounted By:    <none>
Events:
  Type    Reason                  Age   From                         Message
  ----    ------                  ----  ----                         -------
  Normal  ProvisioningSucceeded   48s   persistentvolume-controller  Successfully provisioned volume pvc-29c667db-b103-49f8-9b2f-87ca5d29f751 using kubernetes.io/glusterfs
  Normal  VolumeResizeSuccessful  3s    volume_expand                ExpandVolume succeeded for volume rookieops/glusterfs-pvc

可以看到event信息中有扩展成功。

既然可以扩容，那么可以缩容吗？我们将上面的YAML文件中的storage改小试试

# kubectl apply -f  glusterfs-pvc.yaml 
The PersistentVolumeClaim "glusterfs-pvc" is invalid: spec.resources.requests.storage: Forbidden: field can not be less than previous value

然后报错，不允许缩容。

结论：如果动态PV要进行扩容需要满足以下条件：

• 需要是kubernetes支持的存储，开发能力强的也可以自己开发使其支持第三方存储
• 需要在sc中开启allowVolumeExpansion: true
• 存储设备要有足够的存储能力