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Day 13：StorageClass 有提到 StorageClass 的主要作用就是讓我們可以在建立 PVC 時，動態的幫助我們配置相對應的 PV。而 Day 14：local-path-provisioner
則提到 PVC 建立後，會在 HostPath 建立名稱包含 PVC ID 的資料夾。

PV

基於這些資訊，我想到了可以去觀察 PV 這個元件，這是 PVC gitlab-minio 所屬的 PV 的 Yaml 檔。

apiVersion: v1
kind: PersistentVolume
metadata:
annotations:
  pv.kubernetes.io/provisioned-by: rancher.io/local-path
creationTimestamp: "2024-10-01T14:34:43Z"
finalizers:
- kubernetes.io/pv-protection
name: pvc-de673ad8-35dc-477c-b81e-ecda44dfdc6d
resourceVersion: "4483"
uid: 36bb118f-9f64-4ddb-a23f-2d726cd4fd33
spec:
accessModes:
- ReadWriteOnce
capacity:
  storage: 10Gi
claimRef:
  apiVersion: v1
  kind: PersistentVolumeClaim
  name: gitlab-minio
  namespace: gitlab
  resourceVersion: "4400"
  uid: de673ad8-35dc-477c-b81e-ecda44dfdc6d
hostPath:
  path: /var/local-path-provisioner/pvc-de673ad8-35dc-477c-b81e-ecda44dfdc6d_gitlab_gitlab-minio
  type: DirectoryOrCreate
nodeAffinity:
  required:
    nodeSelectorTerms:
    - matchExpressions:
      - key: kubernetes.io/hostname
        operator: In
        values:
        - local-dev-worker2
persistentVolumeReclaimPolicy: Retain
storageClassName: standard-retain
volumeMode: Filesystem
status:
lastPhaseTransitionTime: "2024-10-01T14:34:43Z"
phase: Bound

觀察上述 Yaml 可以觀察到幾個部分：

1. claimRef
   a. 定義如何與 PVC 進行配對。
2. hostPath
3. nodeAffinity
   a. 定義 PV 會被建立在哪個 Node 上。
4. storageClassName

綜合以上幾點可以得知，這個 PV 是如何定義和 PVC 與 StorageClass 還有 HostPath 之間的關係。

如果將這個 Yaml 改成不指定 Node、不指定對應的 PVC ID，只根據 PVC Name 來配對。再保留使用相同的 HostPath 路徑與 StorageClass。這樣是否在建立新 PVC 時，是否就可以繼承這個些資料了？

以下是我將所有 PV 修改完成的 Yaml：

apiVersion: v1
items:
- apiVersion: v1
  kind: PersistentVolume
  metadata:
    annotations:
      pv.kubernetes.io/provisioned-by: rancher.io/local-path
    name: pvc-2876a885-8908-4f44-b90e-d3f1dd3ee3f5
  spec:
    accessModes:
    - ReadWriteOnce
    capacity:
      storage: 8Gi
    claimRef:
      apiVersion: v1
      kind: PersistentVolumeClaim
      name: data-gitlab-postgresql-0
      namespace: gitlab
    hostPath:
      path: /var/local-path-provisioner/pvc-2876a885-8908-4f44-b90e-d3f1dd3ee3f5_gitlab_data-gitlab-postgresql-0
      type: DirectoryOrCreate
    persistentVolumeReclaimPolicy: Retain
    storageClassName: standard-retain
    volumeMode: Filesystem
- apiVersion: v1
  kind: PersistentVolume
  metadata:
    annotations:
      pv.kubernetes.io/provisioned-by: rancher.io/local-path
    name: pvc-2d31279f-e9c8-45a6-aec9-8141120efce4
  spec:
    accessModes:
    - ReadWriteOnce
    capacity:
      storage: 8Gi
    claimRef:
      apiVersion: v1
      kind: PersistentVolumeClaim
      name: redis-data-gitlab-redis-master-0
      namespace: gitlab
    hostPath:
      path: /var/local-path-provisioner/pvc-2d31279f-e9c8-45a6-aec9-8141120efce4_gitlab_redis-data-gitlab-redis-master-0
      type: DirectoryOrCreate
    persistentVolumeReclaimPolicy: Retain
    storageClassName: standard-retain
    volumeMode: Filesystem
- apiVersion: v1
  kind: PersistentVolume
  metadata:
    annotations:
      pv.kubernetes.io/provisioned-by: rancher.io/local-path
    name: pvc-3e6e871a-d20e-4938-83c1-e092cb96844b
  spec:
    accessModes:
    - ReadWriteOnce
    capacity:
      storage: 50Gi
    claimRef:
      apiVersion: v1
      kind: PersistentVolumeClaim
      name: repo-data-gitlab-gitaly-0
      namespace: gitlab
    hostPath:
      path: /var/local-path-provisioner/pvc-3e6e871a-d20e-4938-83c1-e092cb96844b_gitlab_repo-data-gitlab-gitaly-0
      type: DirectoryOrCreate
    persistentVolumeReclaimPolicy: Retain
    storageClassName: standard-retain
    volumeMode: Filesystem
- apiVersion: v1
  kind: PersistentVolume
  metadata:
    annotations:
      pv.kubernetes.io/provisioned-by: rancher.io/local-path
    name: pvc-de673ad8-35dc-477c-b81e-ecda44dfdc6d
  spec:
    accessModes:
    - ReadWriteOnce
    capacity:
      storage: 10Gi
    claimRef:
      apiVersion: v1
      kind: PersistentVolumeClaim
      name: gitlab-minio
      namespace: gitlab
    hostPath:
      path: /var/local-path-provisioner/pvc-de673ad8-35dc-477c-b81e-ecda44dfdc6d_gitlab_gitlab-minio
      type: DirectoryOrCreate
    persistentVolumeReclaimPolicy: Retain
    storageClassName: standard-retain
    volumeMode: Filesystem
kind: List
metadata:
  resourceVersion: ""
  selfLink: ""

實驗

將 GitLab Helm Release 刪除，再刪除 PVCs、PVs、ConfigMaps、Secrets 後，我先將 PV 建立起來。

kubectl apply -f pv-new.yaml

再將使用昨天相同的指令部署，部署完成後發現，新的 PVC 在建立時，成功繼承這些資料！！！

如果是第一次建立 GitLab，不包含這些 PVC 的資料會發生什麼事？
由於 hostPath 的 type 為 DirectoryOrCreate，所以就算資料夾不存在，它也會自動建立，所以不用擔心。