Skip to main content

Volumes

Configured at the container level. Each container spec must configure its own volume.

Trouble for multi container pods!

A volume gets destroyed with the pod. <-- Is this true?

todo! Test!

tip

A Volume enables safe container restart and allows sharing of data across containers, whereas a PV enables safe Pod termination or restart.

Persistent Volumes

PVs are a large pool of storage that pods can request pieces of

A persistent volume is a large cluster-wide volume , wher ea slice of it is requested by a pod using a Persistent Volume Claim

Modes:

  • ReadOnlyMany
  • ReadWriteOnce
  • ReadWriteMany

Specify the total storage / capacity

apiVersion: v1
kind: PersistentVolume
metadata:
   name: pv-vol1
spec:
   accessModes:
     - ReadWriteOnce
   capacity:
      storage: 1Gi
   awsElasticBlackStore:
      volumeId: {volId}
      fsType: ext4

Persistent Volume Claims​

Admins create PVs, Users create PVCs

K8s will bind a PVC to a PV based on reuqests set on the volume. Every claim is bound to a volume. During the bdining process, k8s tries to find a volume that has sufficient space during the claim. as well as other requirements like Access Mode, Volume Mode, Storage, Class, and labels & selectors.

There is a 1:1 relationship between claims & volumes.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
   name: myclaim
spec:
   accessModes:
     - ReadWriteOnce
   resources:
      requests:
         storage: 500Mi

kubectl get pvc kubectl delete pvc

Reclaim policy​

persistentVolumeReclaimPolicy: Retain Not available for use by any other claims

persistentVolumeReclaimPolicy: Delete Goodbye volume

persistentVolumeReclaimPolicy: Recycle Re-use the existing storage / scrub it, and use it again

Static vs Dynamic Volume Provisioning​

Static: aws ebs create volume

Then create a PV with the ID from the create command

This is where storage classes come in.

Dynamic Provisioning​

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
     name: google-storage
provisioner: kubernetes.io/gce-pd # Or other
parameters:
  ... specific to the storageclass

With this, we don't need a PV definition. The storage class will do it when it is created.

In the PVC Definition, simply add

storageClassName: google-storage

Storage classes create the PV for you!