Local Volumes

Running a stateful application with HwameiStor is super easy.

As an example, we will deploy a MySQL application by creating a local volume.

注意

The yaml file for MySQL is learnt from Kubernetes repo

Verify StorageClass

Make sure the StorageClasses have been created successfully by HwameiStor Operator. And then select one of them to provision the data volume for the application.

$ kubectl get sc hwameistor-storage-lvm-hdd -o yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: hwameistor-storage-lvm-hdd
parameters:
  convertible: "false"
  csi.storage.k8s.io/fstype: xfs
  poolClass: HDD
  poolType: REGULAR
  replicaNumber: "1"
  striped: "true"
  volumeKind: LVM
provisioner: lvm.hwameistor.io
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true

Create StatefulSet

With HwameiStor and its StorageClass ready, a MySQL StatefulSet and its volumes can be deployed by a single command:

$ kubectl apply -f sts-mysql_local.yaml

Please note the volumeClaimTemplates uses storageClassName: hwameistor-storage-lvm-hdd:

spec:
  volumeClaimTemplates:
  - metadata:
      name: data
      labels:
        app: sts-mysql-local
        app.kubernetes.io/name: sts-mysql-local
    spec:
      storageClassName: hwameistor-storage-lvm-hdd
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 1Gi

Please note the minimum PVC size need to be over 4096 blocks, for example, 16MB with 4KB block.

Verify MySQL Pod and PVC/PV

In this example, the pod is scheduled on node k8s-worker-3.

$ kubectl get po -l  app=sts-mysql-local -o wide
NAME                READY   STATUS    RESTARTS   AGE     IP            NODE        
sts-mysql-local-0   2/2     Running   0          3m08s   10.1.15.154   k8s-worker-3

$ kubectl get pvc -l  app=sts-mysql-local
NAME                     STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS                 AGE   VOLUMEMODE
data-sts-mysql-local-0   Bound    pvc-accf1ddd-6f47-4275-b520-dc317c90f80b   1Gi        RWO            hwameistor-storage-lvm-hdd    3m   Filesystem

Verify LocalVolume objects

By listing LocalVolume(LV) objects with the same name as that of the PV, we can see that the local volume is also created on node k8s-worker-3

$ kubectl get lv pvc-accf1ddd-6f47-4275-b520-dc317c90f80b

NAME                                       POOL                   REPLICAS   CAPACITY     ACCESSIBILITY   STATE   RESOURCE   PUBLISHED      AGE
pvc-accf1ddd-6f47-4275-b520-dc317c90f80b   LocalStorage_PoolHDD   1          1073741824                   Ready   -1         k8s-worker-3    3m

[Optional] Scale MySQL out into a 3-node Cluster

HwameiStor supports StatefulSet scaleout. Each pod of the StatefulSet will attach and mount an independent HwameiStor volume.

$ kubectl scale sts/sts-mysql-local --replicas=3

$ kubectl get po -l  app=sts-mysql-local -o wide
NAME                READY   STATUS     RESTARTS   AGE     IP            NODE        
sts-mysql-local-0   2/2     Running    0          4h38m   10.1.15.154   k8s-worker-3
sts-mysql-local-1   2/2     Running    0          19m     10.1.57.44    k8s-worker-2
sts-mysql-local-2   0/2     Init:0/2   0          14s     10.1.42.237   k8s-worker-1

$ kubectl get pvc -l  app=sts-mysql-local -o wide
NAME                     STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS                 AGE     VOLUMEMODE
data-sts-mysql-local-0   Bound    pvc-accf1ddd-6f47-4275-b520-dc317c90f80b   1Gi        RWO            hwameistor-storage-lvm-hdd   3m07s   Filesystem
data-sts-mysql-local-1   Bound    pvc-a4f8b067-9c1d-450f-aff4-5807d61f5d88   1Gi        RWO            hwameistor-storage-lvm-hdd   2m18s   Filesystem
data-sts-mysql-local-2   Bound    pvc-47ee308d-77da-40ec-b06e-4f51499520c1   1Gi        RWO            hwameistor-storage-lvm-hdd   2m18s   Filesystem

$ kubectl get lv
NAME                                       POOL                   REPLICAS   CAPACITY     ACCESSIBILITY   STATE   RESOURCE   PUBLISHED      AGE
pvc-47ee308d-77da-40ec-b06e-4f51499520c1   LocalStorage_PoolHDD   1          1073741824                   Ready   -1         k8s-worker-1   2m50s
pvc-a4f8b067-9c1d-450f-aff4-5807d61f5d88   LocalStorage_PoolHDD   1          1073741824                   Ready   -1         k8s-worker-2   2m50s
pvc-accf1ddd-6f47-4275-b520-dc317c90f80b   LocalStorage_PoolHDD   1          1073741824                   Ready   -1         k8s-worker-3   3m40s