VolumeClaimTemplate:

volumeClaimTemplate:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 30Gi

Official example

https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/#components

apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  selector:
    matchLabels:
      app: nginx # has to match .spec.template.metadata.labels
  serviceName: "nginx"
  replicas: 3 # by default is 1
  minReadySeconds: 10 # by default is 0
  template:
    metadata:
      labels:
        app: nginx # has to match .spec.selector.matchLabels
    spec:
      terminationGracePeriodSeconds: 10
      containers:
      - name: nginx
        image: registry.k8s.io/nginx-slim:0.8
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: "my-storage-class"
      resources:
        requests:
          storage: 1Gi

Elasticsearch helm chart templates/statefulset.yaml

   {{- if .Values.persistence.enabled }}
   volumeClaimTemplates:
   - metadata:
       name: {{ template "elasticsearch.uname" . }}
     {{- if .Values.persistence.labels.enabled }}
       labels:
         release: {{ .Release.Name | quote }}
         chart: "{{ .Chart.Name }}"
         app: "{{ template "elasticsearch.uname" . }}"
         {{- range $key, $value := .Values.labels }}
         {{ $key }}: {{ $value | quote }}
         {{- end }}
     {{- end }}
     {{- with .Values.persistence.annotations  }}
       annotations:
 {{ toYaml . | indent 8 }}
     {{- end }}
     spec:
 {{ toYaml .Values.volumeClaimTemplate | indent 6 }}
   {{- end }}

See also

• Kubernetes storage, storage classes, PersistentVolume (PV), PVC, CSI, kind: StorageClass, kind: PersistentVolumeClaim, kind: PersistentVolume, kubectl [ get | describe | edit ] pvc, volumeClaimTemplates:, kubectl patch pv, FailedMount, Volume Expansion, Volume Cloning, snapshots, ExtraVolumes, NotTriggerScaleUp, volumePVCDataSource, AllowVolumeExpansion, EKS storage, provisioner, Storage Capacity Tracking, VolumeBinding, VolumeClaimTemplate, storage.k8s.io, CKA Storage, DoKC, EmptyDir, Volume populators, storageclass.kubernetes.io