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PV PVC's on GKE clusters

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Ramkumar edited this page Oct 2, 2022 · 12 revisions

The steps to create Storage objects, in general:

  1. Create a Disk
  2. Create a Persistent Volume (PV) on the disk.
  3. Create a Persistent Volume Claim (PVC) against the Persistent Volume (PV).

Note: In GKE, it is also possible to create PVC's directly using those default Storage Classes (without creating disks & PV's).

(1) Create PV/PVC from Disks:

Set the "project" property by:

gcloud config set project handy-freedom-363504

Create Disks:

gcloud compute disks create gke-pv --zone=us-west4-b --size=11GB

WARNING: You have selected a disk size of under [200GB]. This may result in poor I/O performance. For more information, see: https://developers.google.com/compute/docs/disks#performance.
Created [https://www.googleapis.com/compute/v1/projects/handy-freedom-363504/zones/us-west4-b/disks/gke-pv].
NAME: gke-pv
ZONE: us-west4-b
SIZE_GB: 11
TYPE: pd-standard
STATUS: READY

New disks are unformatted. You must format and mount a disk before it
can be used. You can find instructions on how to do this at:

https://cloud.google.com/compute/docs/disks/add-persistent-disk#formatting

List Disks:

gcloud compute disks list

Create PV/PVC from the Peristent Disk

apiVersion: v1
kind: PersistentVolume
metadata:
  name: app-storage
spec:
  storageClassName: "apps"
  capacity:
    storage: 10
  accessModes:
    - ReadWriteOnce
  claimRef:
    namespace: default
    name: app-storage-claim
  gcePersistentDisk:
    pdName: gke-pv
    fsType: ext4
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: app-storage-claim
spec:
  storageClassName: "apps"
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5

kubectl get pv

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                       STORAGECLASS   REASON   AGE
app-storage                                10         RWO            Retain           Bound    default/app-storage-claim   apps                    104s

kubectl get pvc

NAME                STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
app-storage-claim   Bound    app-storage                                10         RWO            apps           3m5s

(2) Create PVC's from Existing Storage Classes provided by GKE

List the existing Storage Classes Provided by GKE

kubectl get sc

NAME                 PROVISIONER             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
premium-rwo          pd.csi.storage.gke.io   Delete          WaitForFirstConsumer   true                   9h
standard (default)   kubernetes.io/gce-pd    Delete          Immediate              true                   9h
standard-rwo         pd.csi.storage.gke.io   Delete          WaitForFirstConsumer   true                   9h

Use one of the above in the below StatefulSet. With the volumeClaimTemplates key name, you can request PVC's from the storage class dynamically.

It will create as many PVC's as required automatically depending upon the requested number of "replicas" for the statefulset.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
spec:
  replicas: 1
  serviceName: mysql
  selector:
    matchLabels:
      app: mysql
  template:
    metadata:
      labels:
        app: mysql
    spec:
      terminationGracePeriodSeconds: 10
      containers:
        - name: mysql
          image: mysql:5.6
          ports:
            - name: tpc
              protocol: TCP
              containerPort: 3306
          env:
            - name: MYSQL_ROOT_PASSWORD
              value: root
          volumeMounts:
            - name: mysql-pvc
              mountPath: /var/lib/mysql
  volumeClaimTemplates:
    - metadata:
        name: mysql-pvc
      spec:
        storageClassName: standard-rwo
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 5Gi

This has created the below PVC now:

kubectl get pvc

NAME                STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
mysql-pvc-mysql-0   Bound    pvc-377f5d0b-988a-4cc2-9e78-15d85b31ad91   5Gi        RWO            standard-rwo   19s

Note:

  1. The name of the PVC is static. It includes, "the template name provided for the PVC","Statefuset Name" and ending with the stetefulset' ordinal#.

  2. Deleting the PVC will also delete the PV it is based on.

kubectl get pv

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                       STORAGECLASS   REASON   AGE
pvc-377f5d0b-988a-4cc2-9e78-15d85b31ad91   5Gi        RWO            Delete           Bound         default/mysql-pvc-mysql-0   standard-rwo            2m8s

It is to demonstrate how flexible this "volumeClaimTemplates" feature is. Scaling the replicas of the Statefulset (from 1 to 2):

kubectl scale  statefulset mysql --replicas 2

It does NOT need to have PV/PVC's pre-created or anything. The required PVC is created automatically.

kubectl get pvc

NAME                STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
mysql-pvc-mysql-0   Bound    pvc-377f5d0b-988a-4cc2-9e78-15d85b31ad91   5Gi        RWO            standard-rwo   5m12s
mysql-pvc-mysql-1   Bound    pvc-c49216b6-ee39-43be-96b9-e81e97b2258f   5Gi        RWO            standard-rwo   46s

kubectl get pv

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS        CLAIM                       STORAGECLASS   REASON   AGE
pvc-377f5d0b-988a-4cc2-9e78-15d85b31ad91   5Gi        RWO            Delete           Bound         default/mysql-pvc-mysql-0   standard-rwo            5m56s
pvc-c49216b6-ee39-43be-96b9-e81e97b2258f   5Gi        RWO            Delete           Bound         default/mysql-pvc-mysql-1   standard-rwo            90s

** (3) Create a PVC with the default Storage class - "pd-standard"**

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: webapps-storage
spec:
  storageClassName: "standard"
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

kubectl get pv

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                       STORAGECLASS   REASON   AGE
pvc-7b439c6f-a4d0-484f-9232-dce0089a2988   5Gi        RWO            Delete           Bound    default/webapps-storage     standard                9s

kubectl get pvc

NAME                STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
webapps-storage     Bound    pvc-7b439c6f-a4d0-484f-9232-dce0089a2988   5Gi        RWO            standard       8s

Using the PVC in a Pod

apiVersion: v1
kind: Pod
metadata:
  name: nginx-app-pod
spec:
  volumes:
    - name: app-storage
      persistentVolumeClaim:
        claimName: webapps-storage
  containers:
    - name: nginx-app-container
      image: nginx
      ports:
        - containerPort: 80
          name: "http-server"
      volumeMounts:
        - mountPath: "/usr/share/nginx/html"
          name: app-storage
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