Editing Tutorials:Persistent volumes on the Kubernetes cluster (section)

=== Local persistent volumes ===

These are persistent volumes which are mapped to special folders of the host filesystem of the node. Each node exposes several persistent volumes which can be claimed. The user can not control exactly which volume is bound to a claim, but can request a minimum size. A persistent volume claim for a local PV is configured like this. Code examples can be found in the subdirectory "kubernetes/example_2" of the tutorial sample code, [[File:Kubernetes_samples.zip|Kubernetes samples]].

'''WARNING: Once a local persistent volume has been bound to a specific node, all pods which make use this volume are forced to also run on this node. This means you have to rely on resources (e.g. GPUs) being available on exactly that particular node.'''

'''NOTE: The storage class "local-ssd" which was previously used for local persistent volumes is now obsolete, since a better driver with automatic provisioning has been installed. From now on, please use "local-path" instead, which will give you a PV on the fastest local device (usually SSD/NVMe RAID). No new volumes of class "local-ssd" can be claimed.''' Please copy over your data from old PVCs if you have the opportunity, or delete old PVCs not in use anymore. As soon as there are no more PVCs of the old class in use, it will be deleted from the cluster. Also, check out "global-datasets" below, which gives you a new opportunity to store large, static datasets on a very fast device.


<syntaxhighlight lang="yaml">
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  # the name of the PVC, we refer to this in the container configuration
  name: tf-mnist-pvc

spec:
  resources:
    requests:
      # storage resource request. This PVC can only be bound to volumes which
      # have at least 8 GiB of storage available.
      storage: 8Gi

  # the requested storage class, see tutorial.
  storageClassName: local-path

  # leave these unchanged, they must match the PV type, otherwise binding will fail
  accessModes:
    - ReadWriteOnce
  volumeMode: Filesystem
</syntaxhighlight>

The following storage classes are configured in the cluster:




When the claim is defined to your satisfaction, apply it like this:

<syntaxhighlight lang="yaml">
> kubectl apply -f pvc.yaml
</syntaxhighlight>

You can check on the status of this (and every other) claim:

<syntaxhighlight lang="yaml">
> kubectl get pvc
NAME           STATUS    VOLUME   CAPACITY   ACCESS MODES   STORAGECLASS   AGE
tf-mnist-pvc   Pending                                      local-path     11s
</syntaxhighlight>

Since the claim has not been used by a container yet, it is not yet bound to a persitent volume (PV).