New to KubeDB? Please start here.
PostgreSQL StorageClass Migration
This guide will show you how to use KubeDB Ops Manager to migrate StorageClass of PostgreSQL database.
Before You Begin
At first, you need to have a Kubernetes cluster, and the
kubectlcommand-line tool must be configured to communicate with your cluster.You must have at least two
StorageClassresources in order to perform a migration.Install
KubeDBoperator in your cluster following the steps here.
To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.
$ kubectl create ns demo
namespace/demo created
Prepare PostgreSQL Database
At first verify that your cluster has at least two StorageClass. Let’s check,
➤ kubectl get storageclass
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
local-path (default) rancher.io/local-path Delete WaitForFirstConsumer false 12d
longhorn driver.longhorn.io Delete Immediate true 12d
longhorn-custom driver.longhorn.io Delete WaitForFirstConsumer true 2d20h
longhorn-static driver.longhorn.io Delete Immediate true 12d
From the above output we can see that we have more than two StorageClass resources. We will now deploy a PostgreSQL database using local-path StorageClass and insert some data into it.
After that, we will apply PostgresOpsRequest to migrate StorageClass from local-path to longhorn-custom.
Both the old and new PVCs should be on the same node. Therefore, the new StorageClass
VOLUMEBINDINGMODEshould beWaitForFirstConsumerif the old one usesWaitForFirstConsumer. If the old one usesImmediateany mode is allowed.
KubeDB implements a Postgres CRD to define the specification of a PostgreSQL database. Below is the Postgres object created in this tutorial.
apiVersion: kubedb.com/v1
kind: Postgres
metadata:
name: sample-postgres
namespace: demo
spec:
version: "13.13"
replicas: 3
standbyMode: Hot
storageType: Durable
storage:
storageClassName: "local-path"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 3Gi
deletionPolicy: WipeOut
$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.8.31/docs/examples/postgres/migration/sample-postgres.yaml
postgres.kubedb.com/sample-postgres created
Now, wait until sample-postgres has status Ready and check the StorageClass,
$ kubectl get postgres,pvc -n demo
NAME VERSION STATUS AGE
sample-postgres 13.13 Ready 101s
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS VOLUMEATTRIBUTESCLASS AGE
persistentvolumeclaim/data-sample-postgres-0 Bound pvc-64cca3c6-85aa-426f-abc3-b300ecfe365a 3Gi RWO local-path <unset> 96s
persistentvolumeclaim/data-sample-postgres-1 Bound pvc-1de36b06-8e32-4e9a-a01b-3b6d7c618688 3Gi RWO local-path <unset> 90s
persistentvolumeclaim/data-sample-postgres-2 Bound pvc-a75bd538-8a71-4f62-8d38-3f4e42ffb225 3Gi RWO local-path <unset> 85s
The database is Ready and all the PersistentVolumeClaim uses local-path StorageClass, Let’s create a table in the primary.
# find the primary pod
$ kubectl get pods -n demo --show-labels | grep primary | awk '{ print $1 }'
sample-postgres-0
# exec into the primary and generate some data
$ kubectl exec -it -n demo sample-postgres-0 -- bash
Defaulted container "postgres" out of: postgres, pg-coordinator, postgres-init-container (init)
sample-postgres-0:/$ psql
psql (13.13)
Type "help" for help.
postgres=# create table hello(id int);
CREATE TABLE
postgres=# insert into hello(id) values(generate_series(1,111111));
INSERT 0 111111
postgres=# select count(*) from hello;
count
--------
111111
(1 row)
Apply StorageMigration Ops-Request
To migrate StorageClass we have to create a PostgresOpsRequest CR with our desired StorageClass. Below is the YAML of the PostgresOpsRequest CR that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: PostgresOpsRequest
metadata:
name: storage-migration
namespace: demo
spec:
type: StorageMigration
databaseRef:
name: sample-postgres
migration:
storageClassName: longhorn-custom
oldPVReclaimPolicy: Delete
Here,
spec.typespecifies that we are performingStorageMigrationoperation.spec.databaseRef.namespecifies that we are performing StorageMigration operation onsample-postgresdatabase.spec.migration.storageClassNamespecifies our desired StorageClassspec.migration.oldPVReclaimPolicyspecifies the reclaim policy of previous persistent volume.
Note: To retain the old PersistentVolume, set
spec.migration.oldPVReclaimPolicytoRetain.
Let’s create the PostgresOpsRequest CR we have shown above,
$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.8.31/docs/examples/postgres/migration/storage-migration.yaml
postgresopsrequest.ops.kubedb.com/storage-migration created
Verify the StorageClass Migrated Successfully
If everything goes well, KubeDB operator will migrate the StorageClass along with the data.
Let’s wait for PostgresOpsRequest to be Successful. Run the following command to watch PostgresOpsRequest CR,
$ watch kubectl get postgresopsrequest -n demo
Every 2.0s: kubectl get postgresopsrequest -n demo
NAME TYPE STATUS AGE
storage-migration StorageMigration Successful 13m
We can see from the above output that the PostgresOpsRequest has succeeded. Let’s verify the StorageClass.
$ kubectl get pvc -n demo
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS VOLUMEATTRIBUTESCLASS AGE
data-sample-postgres-0 Bound pvc-64cca3c6-85aa-426f-abc3-b300ecfe365a 3Gi RWO longhorn-custom <unset> 21m
data-sample-postgres-1 Bound pvc-1de36b06-8e32-4e9a-a01b-3b6d7c618688 3Gi RWO longhorn-custom <unset> 21m
data-sample-postgres-2 Bound pvc-a75bd538-8a71-4f62-8d38-3f4e42ffb225 3Gi RWO longhorn-custom <unset> 21m
The PersistentVolumeClaim StorageClass has changed to longhorn-custom. Now, we will verify that the data remains intact after the StorageMigration operation. Let’s exec into one of the Postgres pod and perform read query.
$ kubectl exec -it -n demo sample-postgres-0 -- bash
Defaulted container "postgres" out of: postgres, pg-coordinator, postgres-init-container (init)
sample-postgres-0:/$ psql
psql (13.13)
Type "help" for help.
postgres=# select count(*) from hello;
count
--------
111111
(1 row)
From the above output we can verify that data remains intact after the StorageMigration operation.
CleanUp
To clean up the Kubernetes resources created by this tutorial, run:
$ kubectl delete postgresopsrequest -n demo storage-migration
$ kubectl delete postgres -n demo sample-postgres
$ kubectl delete ns demo