PersistentVolumeClaim (pvc)

• It's the action of requesting a storage volume (so that it can be attached to a pod)
• The PVC can request a volume from
• A preexisting PV that satisfies the matching criteria
• A defined SC, so that it dynamically creates the PV under the hood
• A PVC can be mounted to multiple pods at the same time, but be careful

PVC Phases

• Pending
• No match to any PV or the SC has not created the PV yet (the case of WaitForFirstConsumer)
• Bound
• A PV has been created it is bound to this PVC

Claim from PV

• It finds an existing PV that satisfies the claim
• If there are multiple matches for the claim, you can use labels to bind to the desired volume
• A small PVC will match to a big PV if it doesn't find a better option
• There is a 1 to 1 relationship between PV and PVC

• PVC must exist in the same namespace of the pod

• Matching Criteria

• Sufficient Capacity
• Access Modes
• Volume Modes
• Storage Class
• Selector

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  resources:
    requests:
      storage: 30Mi # it can match with bigger PVs
  accessModes:
    - ReadWriteOnce

Claim from SC

• Define the storage volume provisioner (SC)

• This way, the PV is created automatically by the StorageClass

• standard: static provisioning

• manual: static provisioning
• storage-class-name: dynamic provisioning

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  storageClassName: ebs-sc
  resources:
    requests:
      storage: 2Gi
  accessModes:
    - ReadWriteOnce

Properties

spec.storageClassName

• Defines dynamic provisioning of volumes by means of an StorageClass (SC)
• When a VPC is created, a PV is then provisioned automatically on the cloud on the fly

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  storageClassName: ebs-sc
  resources:
    requests:
      storage: 4Gi

spec.volumeName

• Explicitly define the PV that should bind this PVC (is the other criteria also match)

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  volumeName: my-pv
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

spec.resources

• It represents the minimum storage resources (e.g., size) the PV should have

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  resources:
    requests:
      storage: 30Mi

spec.accessModes

• It represents the desired access modes the PV should have

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  resources:
    requests:
      storage: 30Mi
  accessModes:
    - ReadWriteOnce

spec.volumeMode

• It represents the volume mode that the PV should have

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: block-claim
spec:
  storageClassName: ebs-sc
  volumeMode: Block
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 4Gi