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MaxScale Volume Expansion

This guide will show you how to use KubeDB Ops-manager operator to expand the volume of MaxScale server.

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 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

Expand Volume of MaxScale

Here, we are going to deploy a MariaDB cluster in replication mode using a supported version by KubeDB operator. Then we are going to apply MariaDBOpsRequest to expand its volume.

Prepare MariaDB Database

At first verify that your cluster has a storage class, that supports volume expansion. Let’s check,

$ kubectl get storageclass
NAME                   PROVISIONER             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
local-path             rancher.io/local-path   Delete          WaitForFirstConsumer   false                  46h
longhorn               driver.longhorn.io      Delete          Immediate              true                   2m27s
longhorn-static        driver.longhorn.io      Delete          Immediate              true                   2m24s

We can see from the output that longhorn storage class has ALLOWVOLUMEEXPANSION field as true. So, this storage class supports volume expansion. We will use this storage class. You can install longhorn from here.

Now, we are going to deploy a MariaDB database with MaxScale in replication mode.

Deploy MariaDB with MaxScale

In this section, we are going to deploy a MariaDB database along with MaxScale with 50Mi volume. Then, in the next section we will expand its volume to 100Mi using MariaDBOpsRequest CRD. Below is the YAML of the MariaDB CR that we are going to create,

apiVersion: kubedb.com/v1
kind: MariaDB
metadata:
  name: mariadb-replication
  namespace: demo
spec:
  version: "10.5.23"
  replicas: 3
  topology:
    mode: MariaDBReplication
    maxscale:
      replicas: 3
      enableUI: true
      storageType: Durable
      storage:
        storageClassName: "longhorn"
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 50Mi
  storageType: Durable
  storage:
    storageClassName: "longhorn"
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.8.31/docs/examples/mariadb/volume-expansion/md-replication.yaml
mariadb.kubedb.com/md-replication created

Now, wait until mariadb-replication has status Ready. i.e,

$ kubectl get mariadb -n demo
NAME             VERSION   STATUS   AGE
md-replication   10.5.23   Ready    2m30s

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

$ kubectl get petset -n demo md-replication-mx -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"50Mi"

$ kubectl get pv -n demo
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                           STORAGECLASS   VOLUMEATTRIBUTESCLASS   REASON   AGE
pvc-27e4f4b2-289b-44bb-97a2-729d9420f668   1Gi        RWO            Delete           Bound    demo/data-md-replication-2      longhorn       <unset>                          3m48s
pvc-2df9a141-5d32-4c92-b0ec-a8043975c2ae   1Gi        RWO            Delete           Bound    demo/data-md-replication-1      longhorn       <unset>                          3m48s
pvc-7609183e-f9a5-4177-b260-0d24796fb04c   1Gi        RWO            Delete           Bound    demo/data-md-replication-0      longhorn       <unset>                          3m48s
pvc-96449ed7-305e-4857-a2b6-6eda33c99207   50Mi       RWO            Delete           Bound    demo/data-md-replication-mx-2   longhorn       <unset>                          3m51s
pvc-c1424029-4a52-4ff4-9888-14d5e7b4fb61   50Mi       RWO            Delete           Bound    demo/data-md-replication-mx-0   longhorn       <unset>                          3m51s
pvc-d12d301c-58bd-4c59-bd5a-d9167df2b53d   50Mi       RWO            Delete           Bound    demo/data-md-replication-mx-1   longhorn       <unset>                          3m51s

You can see that MaxScale petset has 50Mi storage, and the capacity of the MaxScale persistent volumes are also 50Mi.

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

Volume Expansion

Here, we are going to expand the volume of the MaxScale cluster.

Create MariaDBOpsRequest

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

apiVersion: ops.kubedb.com/v1alpha1
kind: MariaDBOpsRequest
metadata:
  name: maxscale-volume-expansion
  namespace: demo
spec:
  type: VolumeExpansion
  databaseRef:
    name: md-replication
  volumeExpansion:
    mode: Online
    maxscale: 100Mi

Here,

spec.type specifies that we are performing VolumeExpansion on our database.
spec.databaseRef.name specifies that we are performing volume expansion operation on md-replication database.
spec.volumeExpansion.mode specifies the desired volume expansion mode (Online or Offline). Storageclass longhorn supports Online volume expansion.
spec.volumeExpansion.maxscale specifies the desired volume size of maxscale server.

Note: If the Storageclass you are using doesn’t support Online Volume Expansion, Try offline volume expansion by using spec.volumeExpansion.mode:"Offline". The pods need to be restarted during offline volume expansion.

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.8.31/docs/examples/mariadb/volume-expansion/maxscale-volume-expansion.yaml
mariadbopsrequest.ops.kubedb.com/maxscale-volume-expansion created

Verify MaxScale volume expanded successfully

If everything goes well, KubeDB Ops-manager operator will update the volume size of MaxScale object and related PetSets and Persistent Volumes.

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

$ kubectl get mariadbopsrequest -n demo
NAME                        TYPE              STATUS       AGE
maxscale-volume-expansion   VolumeExpansion   Successful   3m

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

$ kubectl describe mariadbopsrequest -n demo maxscale-volume-expansion
Name:         maxscale-volume-expansion
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MariaDBOpsRequest
Metadata:
  Creation Timestamp:  2025-07-23T06:46:12Z
  Generation:          1
  Resource Version:    96939
  UID:                 c33c6a08-2514-4818-932e-f4460bd612a7
Spec:
  Apply:  IfReady
  Database Ref:
    Name:  md-replication
  Type:    VolumeExpansion
  Volume Expansion:
    Maxscale:  100Mi
    Mode:      Online
Status:
  Conditions:
    Last Transition Time:  2025-07-23T06:46:12Z
    Message:               Controller has started to Progress the MariaDBOpsRequest: demo/maxscale-volume-expansion
    Observed Generation:   1
    Reason:                Running
    Status:                True
    Type:                  Running
    Last Transition Time:  2025-07-23T06:46:20Z
    Message:               all pvc; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  AllPvc
    Last Transition Time:  2025-07-23T06:46:20Z
    Message:               is pvc patch; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  IsPvcPatch
    Last Transition Time:  2025-07-23T06:47:10Z
    Message:               delete pvc; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  DeletePvc
    Last Transition Time:  2025-07-23T06:47:15Z
    Message:               Online Volume Expansion performed successfully in MaxScale pod for MariaDBOpsRequest: demo/maxscale-volume-expansion
    Observed Generation:   1
    Reason:                VolumeExpansionSucceeded
    Status:                True
    Type:                  VolumeExpansion
    Last Transition Time:  2025-07-23T06:47:15Z
    Message:               Controller has successfully expand the volume of MaxScale: demo/maxscale-volume-expansion
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason                              Age   From                         Message
  ----     ------                              ----  ----                         -------
  Normal   Starting                            15m   KubeDB Ops-manager Operator  Start processing for MariaDBOpsRequest: demo/maxscale-volume-expansion
  Normal   Starting                            15m   KubeDB Ops-manager Operator  Pausing MariaDB databse: demo/md-replication
  Normal   Successful                          15m   KubeDB Ops-manager Operator  Successfully paused MariaDB database: demo/md-replication for MariaDBOpsRequest: maxscale-volume-expansion
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  is pvc patch; ConditionStatus:True  15m   KubeDB Ops-manager Operator  is pvc patch; ConditionStatus:True
  Warning  is pvc patch; ConditionStatus:True  15m   KubeDB Ops-manager Operator  is pvc patch; ConditionStatus:True
  Warning  is pvc patch; ConditionStatus:True  15m   KubeDB Ops-manager Operator  is pvc patch; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       15m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       14m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  delete pvc; ConditionStatus:True    14m   KubeDB Ops-manager Operator  delete pvc; ConditionStatus:True
  Warning  all pvc; ConditionStatus:True       14m   KubeDB Ops-manager Operator  all pvc; ConditionStatus:True
  Warning  delete pvc; ConditionStatus:True    14m   KubeDB Ops-manager Operator  delete pvc; ConditionStatus:True
  Normal   Successful                          14m   KubeDB Ops-manager Operator  Online Volume Expansion performed successfully in MaxScale pod for MariaDBOpsRequest: demo/maxscale-volume-expansion
  Normal   Starting                            14m   KubeDB Ops-manager Operator  Updating MaxScale storage
  Normal   Successful                          14m   KubeDB Ops-manager Operator  Successfully updated MaxScale storage
  Normal   Starting                            14m   KubeDB Ops-manager Operator  Resuming MariaDB database: demo/md-replication
  Normal   Successful                          14m   KubeDB Ops-manager Operator  Successfully resumed MariaDB database: demo/md-replication
  Normal   Successful                          14m   KubeDB Ops-manager Operator  Controller has Successfully expand the volume of MaxScale: demo/md-replication

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

$ kubectl get petset -n demo md-replication-mx -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"100Mi"

$ kubectl get pv -n demo
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                           STORAGECLASS   VOLUMEATTRIBUTESCLASS   REASON   AGE
pvc-27e4f4b2-289b-44bb-97a2-729d9420f668   1Gi        RWO            Delete           Bound    demo/data-md-replication-2      longhorn       <unset>                          34m
pvc-2df9a141-5d32-4c92-b0ec-a8043975c2ae   1Gi        RWO            Delete           Bound    demo/data-md-replication-1      longhorn       <unset>                          34m
pvc-7609183e-f9a5-4177-b260-0d24796fb04c   1Gi        RWO            Delete           Bound    demo/data-md-replication-0      longhorn       <unset>                          34m
pvc-96449ed7-305e-4857-a2b6-6eda33c99207   100Mi      RWO            Delete           Bound    demo/data-md-replication-mx-2   longhorn       <unset>                          34m
pvc-c1424029-4a52-4ff4-9888-14d5e7b4fb61   100Mi      RWO            Delete           Bound    demo/data-md-replication-mx-0   longhorn       <unset>                          34m
pvc-d12d301c-58bd-4c59-bd5a-d9167df2b53d   100Mi      RWO            Delete           Bound    demo/data-md-replication-mx-1   longhorn       <unset>                          34m

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

Cleaning Up

To clean up the Kubernetes resources created by this tutorial, run:

$ kubectl delete mariadb -n demo md-replication
$ kubectl delete mariadbopsrequest -n demo maxscale-volume-expansion
$ kubectl delete ns demo

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