⚠️ Deprecation notice

This preview integration of IoT Edge 1.x and Kubernetes will not be made generally available, and is no longer supported. The recommended way to run IoT Edge 1.x on Kubernetes is noted in the product's official docs

Persistent storage

💡 For Azure Stack Edge specific guidance, please see the ASE section.

Use Kubernetes persistent volumes.

If your module needs to persist non-ephemeral data, be sure to use Persistent Volumes. In the namespace for your IoT Edge workloads, pre-create Persistent Volume Claims (PVC) for modules that require persistence.

Always configure iotedged with a PVC

At a minimum, one PVC is required for iotedged to store its crypto material. On multi-node k8s clusters this PVC cannot be backed by host local storage as its stored state needs to be attached to iotedged pod even if it gets moved to a different agent node.

If a new instance of iotedged pod cannot access its previously created state, it will create new state and starting running. However, all previously running modules will fail and will need to be manually restarted to sync up with the new iotedged instance.

When installing iotedged into the cluster, simply reference the pre-created PVC in the helm install command like so:

helm install --repo https://edgek8s.blob.core.windows.net/staging pv-iotedged-example edge-kubernetes \
  --namespace pv-iotedged \
  --set "iotedged.data.persistentVolumeClaim.name=replace-with-PVC-name" \
  --set "provisioning.deviceConnectionString=$connStr"

Configure edgeHub with a PVC to avoid message loss

edgeHub always persists messages before sending an ack to the sender. This is what enables offline store-and-forward functionality. If edgeHub is not configured with a persistent volume for its message store and it restarts (either on the same node or different node) any undelivered messages stored by the older instance are lost.

If your scenario requires no message loss be sure to configure edgeHub with a PVC. On a multi-node cluster, this persistent volume should be backed by non-host-local storage.

Configure modules' persistent storage using createOption extensions

Rather than rely on Docker API translations, it is simplest to use createOption extensions to assign pre-created PVCs to modules. The technique is demonstrated by this tutorial.

ReadWriteOnce volumes need additional configuration

Volumes can have different access modes.

For ReadWriteOnce volumes deployment strategy should be set to Recreate. For more details, see Deployment strategy guidance

Some StorageClasses may need custom security context

fsGroup and runAsUser might be need to be set for some storage classes to avoid permission errors when accessing the persistent volume. For example, the following securityContext setting were required for the Blob Storage module to work with Longhorn volumes on K3s:

  "k8s-experimental": {
    "securityContext": {
      "fsGroup": "3000",
      "runAsUser": "1000"