GKE how to use existing compute engine disk as persistent volumes?

Question

I might have to rebuild the GKE cluster but the compute engine disks won't be delete and needs to be re-used as persistent volumes for the pods. I haven't found a documentation showing how to link the existing GCP compute engine disk as persistent volumes for the pods.

Is it possible to use the existing GCP compute engine disks with GKE storage class and Persistent volumes?

You want to use one disk for a few VMs like multi-writer or more like moving Volume Snapshot ? — PjoterS
I meant something like this.. stackoverflow.com/a/48655642/8445363 Does it work? It looks like it might. — John

PjoterS PjoterS · Accepted Answer · 2021-03-17T10:26:14

Yes, it's possible to reuse Persistent Disk as Persistent Volume for another clusters, however there is one limitation:

The persistent disk must be in the same zone as the cluster nodes.

If PD will be in a different zone, the cluster will not find this disk.

In Documentation Using preexisting persistent disks as PersistentVolumes you can find information and examples how to reuse persistent disks.

If you didn't create Persistent Disk yet, you can create it based on Creating and attaching a disk documentation. For this tests, I've used below disk:

gcloud compute disks create pd-name \
  --size 10G \
  --type pd-standard \
  --zone europe-west3-b

If you will create PD with less than 200G you will get below Warning, everything depends on your needs. In zone europe-west3-b, pd-standard type can have storage between 10GB - 65536GB.

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/com
pute/docs/disks#performance.

Keep in mind that you might get different types of Persistent Disk on different zones. For more details you can check Disk Types documentation or run $ gcloud compute disk-types list.

Once you have Persistent Disk you can create PersistentVolume and PersistentVolumeClaim.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv
spec:
  storageClassName: "test"
  capacity:
    storage: 10G
  accessModes:
    - ReadWriteOnce
  claimRef:
    namespace: default
    name: pv-claim
  gcePersistentDisk:
    pdName: pd-name
    fsType: ext4
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pv-claim
spec:
  storageClassName: "test"
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10G
---
kind: Pod
apiVersion: v1
metadata:
  name: task-pv-pod
spec:
  volumes:
    - name: task-pv-storage
      persistentVolumeClaim:
       claimName: pv-claim
  containers:
    - name: task-pv-container
      image: nginx
      ports:
        - containerPort: 80
          name: "http-server"
      volumeMounts:
        - mountPath: "/usr/data"
          name: task-pv-storage

Tests

$ kubectl get pv,pvc,pod
NAME                  CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM              STORAGECLASS   REASON   AGE
persistentvolume/pv   10G        RWO            Retain           Bound    default/pv-claim   test                    22s

NAME                             STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
persistentvolumeclaim/pv-claim   Bound    pv       10G        RWO            test           22s

NAME              READY   STATUS    RESTARTS   AGE
pod/task-pv-pod   1/1     Running   0          21s

Write some information to disk

$ kubectl exec -ti task-pv-pod -- bin/bash
root@task-pv-pod:/# cd /usr/share/nginx/html
root@task-pv-pod:/usr/share/nginx/html# echo "This is test message from Nginx pod" >> message.txt

Now I removed all previous resources: pv, pvc and pod.

$ kubectl get pv,pvc,pod
No resources found

Now If I would recreate pv, pvc with small changes in pod, for example busybox.

  containers:
    - name: busybox
      image: busybox
      command: ["/bin/sh"]
      args: ["-c", "while true; do echo hello; sleep 10;done"]
      volumeMounts:
        - mountPath: "/usr/data"
          name: task-pv-storage

It will be rebound

$ kubectl get pv,pvc,po
NAME                  CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM              STORAGECLASS   REASON   AGE
persistentvolume/pv   10G        RWO            Retain           Bound    default/pv-claim                           43m

NAME                             STATUS   VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
persistentvolumeclaim/pv-claim   Bound    pv       10G        RWO                           43m

NAME          READY   STATUS    RESTARTS   AGE
pod/busybox   1/1     Running   0          3m43s

And in the busybox pod I will be able to find Message.txt.

$ kubectl exec -ti busybox -- bin/sh
/ # cd usr
/ # cd usr/data
/usr/data # ls
lost+found   message.txt
/usr/data # cat message.txt 
This is test message from Nginx pod

As additional information, you won't be able to use it in 2 clusters in the same time, if you would try you will get error:

AttachVolume.Attach failed for volume "pv" : googleapi: Error 400: RESOURCE_IN_USE_B
Y_ANOTHER_RESOURCE - The disk resource 'projects/<myproject>/zones/europe-west3-b/disks/pd-name' is already being used by 'projects/<myproject>/zones/europe-west3-b/instances/gke-cluster-3-default-pool-bb545f05-t5hc'

GKE how to use existing compute engine disk as persistent volumes?

1 Answers

Tests