VolumeClaimTemplate
- Docker & Kubernetes course
- Advanced
- Lesson 16/70
- 4 min
Learn persistent storage with volumeClaimTemplates.
VolumeClaimTemplate
volumeClaimTemplates is a template for a separate PersistentVolumeClaim (PVC) for each pod. A 3-replica StatefulSet creates the PVCs data-db-0, data-db-1, data-db-2. Even if a pod is deleted, the PVC remains and the new pod attaches to the same PVC:
spec:
template:
spec:
containers:
- name: postgres
image: postgres:16
volumeMounts:
- name: data
mountPath: /var/lib/postgresql/data
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes: ["ReadWriteOnce"]
resources:
requests:
storage: 10GiSeeing the PVCs
PVC names have the form template-name-pod-name. Each is bound to a PersistentVolume (Bound):
$ kubectl get pvc -l app=db
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS
data-db-0 Bound pvc-3f2a… 10Gi RWO standard
data-db-1 Bound pvc-8d1e… 10Gi RWO standard
data-db-2 Bound pvc-c4b7… 10Gi RWO standardWhen scaled down (3 → 2), data-db-2 isn't deleted; when scaled up again, db-2 returns with the same data.
Practice Add persistent storage
Write a StatefulSet's volumeClaimTemplates section (starting with volumeClaimTemplates:): template name data; accessModes: ["ReadWriteOnce"]; resources.requests.storage: 10Gi.
Starter code
# buraya yazSample solution
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes: ["ReadWriteOnce"]
resources:
requests:
storage: 10GiExpected output
statefulset.apps/db created $ kubectl get pvc NAME STATUS CAPACITY ACCESS MODES data-db-0 Bound 10Gi RWO
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 By default, what happens to the PVCs when the StatefulSet is deleted?
- They are deleted immediately
- They move to another StatefulSet
- They are emptied
- They stay; they must be deleted by hand, to protect the data Correct answer
Explanation: persistentVolumeClaimRetentionPolicy can change this behaviour.
2 Define the PVC template for each pod.
spec:
____:
- metadata:
name: dataspec:
volumeClaimTemplates:
- metadata:
name: dataExplanation: volumeClaimTemplates is specific to StatefulSets.
3 Match.
| Term | Meaning |
|---|---|
volumeClaimTemplates |
PVC per pod |
data-db-0 |
PVC name |
ReadWriteOnce |
Single node writes |
Bound |
Bound to a PV |