Does re-deploying kubernetes statefulset preserve persistent volume claim?

Question

We have a kubernetes statefulset with a persistent volume claim for storage class "zookeeper"

There are 6 persistent volumes of storage class "zookeeper"

The deployment is done using a Helm chart. When I first install the helm chart with 3 replica count, the statefulset uses say, Pv1,Pv2 and Pv3. All running ok.

Delete purge the helm chart.

Re-install the same Helm chart with same number of replicas, 3 This time will the statefulset chose the same Persistent volumes, Pv1, Pv2 and Pv3 or will it choose any random Pv's from the 6 Pv's. This is important because across deployments, if the persistent volume changes, the zookeeper "myid" is messed-up.

Is your StatefulSet making the claim or you do it separately? — suren

DT. DT. · Accepted Answer · 2020-02-13T09:22:08

StatefulSet provides a key named as volumeClaimTemplates using that, you can request the PVC from the storage class dynamically. The volumeClaimTemplates will provide stable storage using PersistentVolumes provisioned by a PersistentVolume Provisioner.

volumeClaimTemplates:
- metadata:
    name: my-pv
  spec:
    accessModes: 
      - ReadWriteMany
    resources:
      requests:
        storage: 1Gi

When you have multiple replica, you will see the pods are created one by one sequentially, and the PVC is requested during the pod creation.The PVC naming is combination of volumeClaimTemplate name + pod-name + order number.

For example, we will have the following PVCs naming

my-pv-app-0
my-pv-app-1
.. and so on

The volume is mount to the respective pod in order there after any restart by scaling operation on StatefulSet will not delete the volumes associated with the StatefulSet.

Does re-deploying kubernetes statefulset preserve persistent volume claim?

1 Answers