Volumes in Kubernetes need to meet three criteria’s:
- Outlives the lifecycle of the Pods
- It should not be tied to a Cluster Node
- Should be able to survive an Cluster Crash
Persistent Volumes
Allows to attach storage to the cluster/ Pod
Storage can be either Local (Node HDD) or External (Cloud Storage/ NFS)
Creating volume in K8s does not provision actual storage space (It is only metadata)
The actual storage needs to be managed and created separately
Volumes are tied to the lifecycle of the Pod
All the containers in a Pod can access the volume
They are not namespaced and is available to all resources on the cluster
Local Volumes : Will be tied to a specific node and cannot survive a cluster crash
For DB data it is always recommended to use remote storage
Persistent Volume Claim (PVC)
For a Pod (application) to use the Volume it needs to Claim the volume
In the PVC config the characteristics of the Volume that is required is specified and the Volume that matches the PVC is selected
In the Pod config the PVC to be used needs to be specified
PVC has to be present in the same namespace as the Pod
Once the Pod has access to the Volume it needs to be mounted to the Pod in order for it to be accessible
Storage Class
Allows to provision Persistent Storage Dynamically when PVC claims it
The Storage Backend is defined using the provider attribute
