Deploying, Scaling, and Monitoring Kubernetes Storage

Introduction to Kubernetes

Frank Heilmann

Platform Architect and Freelance Instructor

Persistent Volumes and Persistent Volume Claims

Fundamental Objects for storage: Persistent Volumes (PV), maintained in parallel to Pods
PVs are mapped to Pods using Persistent Volume Claims (PVC)
A mapped PV allows data persistence when the Pod is stopped, killed, or restarted
PVs enable the separation of storage and compute

Storage Classes

PVs: provisioned either
- manually by an Kubernetes admin
- dynamically by regular user
Dynamic provisioning happens via Storage Classes (SC) without human intervention
Storage Classes (SC):
- defined by Kubernetes admin
- different types (different latency, e.g., SDD vs HDD, different backup strategies)
If in doubt, use Storage Classes ;-)

Putting it all together

There are only three objects that make storage work:
- PersistentVolume
- PersistentVolumeClaim
- StorageClass
A Pod with demand for persisted data uses a PersistentVolumeClaim
This PVC has Kubernetes create a PersistentVolume for the Pod
This PersistentVolume is mapped to the claiming Pod
A named StorageClass is used, which defines details like latency and backup strategy of the PV
This PersistentVolume survives (together with stored data), even when the Pod is terminated

Manifest Snippets

Pod with PersistentVolume

apiVersion: v1
kind: Pod
...

spec:
  containers:
  ...
    volumeMounts:
    - name: pv-mydata
      mountPath: /mydata

  volumes:
  - name: pv-mydata
    persistentVolumeClaim:
      claimName: datacamp-pvc

PersistentVolumeClaim with StorageClass

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: datacamp-pvc

spec:
  storageClassName: "standard"
  accessModes:
  - ReadWriteOnce

  resources:
    requests:
      storage: 5Gi

"kubectl" Commands For Storage

kubectl offers a complete set of commands to create and monitor Kubernetes Storage
Examples:
- kubectl get sc lists all available Storage Classes
- kubectl get pvc lists all deployed Persistent Volume Claimes
- kubectl get pv lists all deployed Persistent Volumes
- As usual, kubectl apply -f <manifest> can be used to deploy storage resources that are declared in Manifests.

Let's practice!

Introduction to Kubernetes