Kubernetes卷中的AccessModes是什么

Question

我试图理解KubernetesPersistentVolumes的访问模式。

根据Kubernetes文档，访问模式为：

ReadWriteOnce -- the volume can be mounted as read-write by a single node
ReadOnlyMany -- the volume can be mounted read-only by many nodes
ReadWriteMany -- the volume can be mounted as read-write by many nodes

卷插件hostpath支持readwriteonce

有人能解释一下这里发生了什么吗？如果可能的话，请给我提供例子/博客，看看RWO、RWX、ROX之间的区别？大多数的博客，只是简单地介绍了PV、PVC和访问方式。

apiVersion: v1
kind: Pod
metadata:
  name: pod2
spec:
  nodeName: controlplane
  containers:
  - image: nginx
    name: pod2
    volumeMounts:
      - name: vol
        mountPath: /usr/share/nginx/html
  volumes:
  - name: vol
    persistentVolumeClaim:
      claimName: pvc
---
apiVersion: v1
kind: Pod
metadata:
  name: pod1
spec:
  nodeName: worker1
  containers:
  - image: nginx
    name: pod1
    volumeMounts:
      - name: vol
        mountPath: /usr/share/nginx/html
  volumes:
  - name: vol
    persistentVolumeClaim:
      claimName: pvc
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: /tmp/test
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

Answer 1

>

请注意，您不应该在控制平面上运行pods，因此您应该在yaml文件中用nodename:controlplane替换nodename:worker2。通常您需要使用容忍来在控制平面上运行pod，因为它有一个污点，无法在其上运行常规pod...

我在Google Kubernetes Engine(gke)上尝试了yaml，我不得不替换nodename字段来使其工作：

diff example.yaml example-gke.yaml 
6c6
<   nodeName: controlplane
---
>   nodeName: gke-qserv-dev-worker-pool-a64a-01bc5238-3zl9 
23c23
<   nodeName: worker1
---
>   nodeName: gke-qserv-dev-worker-pool-a64a-01bc5238-23t3 

正如您所看到的，k8s拒绝创建pod2:

kubectl get pods
NAME                                   READY   STATUS              RESTARTS   AGE
pod1                                   1/1     Running             0          6m27s
pod2                                   0/1     ContainerCreating   0          6m27s

kubectl describe pod pod2 | tail -n 1
  Warning  FailedAttachVolume  7m28s                 attachdetach-controller                                Multi-Attach error for volume "pvc-2fb657ce-4678-4e92-9f64-e4b46b9a3ec7" Volume is already used by pod(s) pod1