KubeDB

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Hazelcast Volume Expansion

This guide will show you how to use KubeDB Ops-manager operator to expand the volume of a Hazelcast database.

Before You Begin

  • At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster.

  • You must have a StorageClass that supports volume expansion.

  • Install KubeDB Provisioner and Ops-manager operator in your cluster following the steps here.

  • You should be familiar with the following KubeDB concepts:

To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in docs/examples/hazelcast folder in GitHub repository kubedb/docs.

Expand Volume of Hazelcast Database

Here, we are going to expand the volume of a Hazelcast database.

Deploy Hazelcast Database

In this section, we are going to deploy a Hazelcast database with 1Gi storage and then we will expand its storage. Below is the YAML of the Hazelcast CR that we are going to create,

apiVersion: kubedb.com/v1alpha2
kind: Hazelcast
metadata:
  name: hz-prod
  namespace: demo
spec:
  deletionPolicy: WipeOut
  licenseSecret:
    name: hz-license-key
  replicas: 2
  version: 5.5.2
  storage:
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 2Gi

Let’s create the Hazelcast CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2026.5.18-rc.0/docs/examples/hazelcast/volume-expansion/hazelcast.yaml
hazelcast.kubedb.com/hz-prod created

Now, wait until hz-prod has status Ready. i.e,

$ kubectl get hz -n demo
NAME             TYPE            VERSION   STATUS   AGE
hz-prod    kubedb.com/v1alpha2   5.2.2     Ready    3m

Let’s check volume size from statefulset, and from the persistent volume,

$ kubectl get statefulset -n demo hz-prod -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"1Gi"

$ kubectl get pv -o json | jq '.items[].spec.capacity.storage'
"1Gi"
"1Gi"

You can see the statefulset has 1Gi storage, and the capacity of all the persistent volumes are 1Gi.

We are now ready to apply the HazelcastOpsRequest CR to expand the volume of this database.

Expanding Storage Size

Here, we are going to expand the volume of the database.

Create HazelcastOpsRequest

In order to expand the volume of the database, we have to create a HazelcastOpsRequest CR with our desired size. Below is the YAML of the HazelcastOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: HazelcastOpsRequest
metadata:
  name: hz-volume-expansion
  namespace: demo
spec:
  type: VolumeExpansion
  databaseRef:
    name: hz-prod
  volumeExpansion:
    hazelcast: 2Gi
    mode: Online

Here,

  • spec.databaseRef.name specifies that we are performing volume expansion operation on hz-prod database.
  • spec.type specifies that we are performing VolumeExpansion on our database.
  • spec.volumeExpansion.hazelcast specifies the desired size of the volume after expansion.

Let’s create the HazelcastOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2026.5.18-rc.0/docs/examples/hazelcast/volume-expansion/ops.yaml
hazelcastopsrequest.ops.kubedb.com/hz-volume-expansion created

Verify Hazelcast volume expanded successfully

If everything goes well, KubeDB Ops-manager operator will expand the volume of Hazelcast object and related statefulsets and Pods.

Let’s wait for HazelcastOpsRequest to be Successful. Run the following command to watch HazelcastOpsRequest CR,

$ kubectl get hazelcastopsrequest -n demo
NAME                  TYPE              STATUS       AGE
hz-volume-expansion   VolumeExpansion   Successful   3m2s

We can see from the above output that the HazelcastOpsRequest has succeeded. If we describe the HazelcastOpsRequest we will get an overview of the steps that were followed to expand the database volume.

$ kubectl describe hazelcastopsrequest -n demo hz-volume-expansion
Name:         hz-volume-expansion
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         HazelcastOpsRequest
Metadata:
  Creation Timestamp:  2025-08-19T13:11:56Z
  Generation:          1
  Resource Version:    5498537
  UID:                 1141abd1-aa25-4beb-837b-69a6d577920f
Spec:
  Apply:  IfReady
  Database Ref:
    Name:  hz-prod
  Type:    VolumeExpansion
  Volume Expansion:
    Hazelcast:  2Gi
    Mode:       Online
Status:
  Conditions:
    Last Transition Time:  2025-08-19T13:11:56Z
    Message:               Hazelcast ops-request has started to expand volume of hazelcast nodes.
    Observed Generation:   1
    Reason:                VolumeExpansion
    Status:                True
    Type:                  VolumeExpansion
    Last Transition Time:  2025-08-19T13:12:29Z
    Message:               successfully deleted the statefulSets with orphan propagation policy
    Observed Generation:   1
    Reason:                OrphanStatefulSetPods
    Status:                True
    Type:                  OrphanStatefulSetPods
    Last Transition Time:  2025-08-19T13:12:09Z
    Message:               get statefulset; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  GetStatefulset
    Last Transition Time:  2025-08-19T13:12:09Z
    Message:               delete statefulset; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  DeleteStatefulset
    Last Transition Time:  2025-08-19T13:15:39Z
    Message:               successfully updated PVC sizes
    Observed Generation:   1
    Reason:                VolumeExpansionSucceeded
    Status:                True
    Type:                  VolumeExpansionSucceeded
    Last Transition Time:  2025-08-19T13:12:39Z
    Message:               get pvc; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  GetPvc
    Last Transition Time:  2025-08-19T13:12:39Z
    Message:               patch pvc; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  PatchPvc
    Last Transition Time:  2025-08-19T13:15:29Z
    Message:               compare storage; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  CompareStorage
    Last Transition Time:  2025-08-19T13:15:49Z
    Message:               successfully reconciled the Hazelcast resources
    Observed Generation:   1
    Reason:                UpdateStatefulSets
    Status:                True
    Type:                  UpdateStatefulSets
    Last Transition Time:  2025-08-19T13:16:09Z
    Message:               StatefulSet is recreated
    Observed Generation:   1
    Reason:                ReadyStatefulSets
    Status:                True
    Type:                  ReadyStatefulSets
    Last Transition Time:  2025-08-19T13:15:59Z
    Message:               get stateful set; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  GetStatefulSet
    Last Transition Time:  2025-08-19T13:15:59Z
    Message:               Successfully completed volumeExpansion for Hazelcast
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:                    <none>

Now, we are going to verify from the statefulset, and the PersistentVolume whether the volume of the database has expanded to meet the desired state, Let’s check,

$ kubectl get statefulset -n demo hz-prod -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"2Gi"

$ kubectl get pv -o json | jq '.items[].spec.capacity.storage'
"2Gi"
"2Gi"

The above output verifies that we have successfully expanded the volume of the Hazelcast database.

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl delete hazelcastopsrequest -n demo hz-volume-expansion
kubectl delete hazelcast -n demo hz-prod
kubectl delete ns demo

Next Steps

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