Feature labels are a powerful and flexible way to control storage features.

Applying specific feature labels triggers compression, replication and other storage features. No feature labels are present by default.

Ondat Node labels

Nodes do not have any feature labels present by default. When Ondat is run within Kubernetes, the Ondat API Manager syncs any Kubernetes node labels to the corresponding Ondat node. The Kubernetes node labels act as the “source of truth”, so labels should be applied to the Kubernetes nodes rather than to Ondat nodes. This is because the Kubernetes node labels overwrite the Ondat node labels on sync.

Feature Label Values Description
Compute only true / false Specifies whether a node should be computeonly where it only acts as a client and does not host volume data locally, otherwise the node is hyperconverged (the default), where the node can operate in both client and server modes.

You can set the compute-only label on the Kubernetes node and the label will be synced to the Ondat node (labels take an eventual consistency reconciliation time of up to a minute (or less)).

kubectl label node $NODE

Ondat Volume labels

Volumes do not have any feature labels present by default.

⚠️ The encryption, caching and compression labels can only apply at provisioning time, they can’t be changed during execution.

Feature Label Values Description
Caching true / false Switches off caching.
Compression true / false Switches off compression of data at rest and in transit (compression is not enabled by default to maximise performance).
Encryption true / false Encrypts the contents of the volume. For each volume, a key is automatically generated, stored, and linked with the PVC.
Failure Mode hard, soft, alwayson or integers [0, 5] Sets the failure mode for a volume, either explicitly using a failure mode or implicitly using a replica threshold. The default setting of a failure mode is hard.
Replication integers [0, 5] Sets the number of replicas i.e full copies of the data across nodes. Typically 1 or 2 replicas is sufficient (2 or 3 instances of the data); latency implications need to be assesed when using more than 2 replicas.
Topology-Aware Placement true / false Enables Topology-Aware Placement
Topology Domain Key custom region Define the failure domain for the node by using a custom key. If you don’t define a custom key, the label defaults to the value.

To create a volume with a feature label, choose one of the following options:

  • Option 1: PVC Label

    Add the label in the PVC definition, for instance:

    apiVersion: v1
    kind: PersistentVolumeClaim
      name: pvc-3
      labels: "1" # Label <-----
      storageClassName: "storageos"
        - ReadWriteOnce
          storage: 1G
  • Option 2: Set label in the StorageClass

    Any PVC using the StorageClass inherits the label. The PVC label takes precedence over the StorageClass parameters.

    kind: StorageClass
      name: storageos-replicated
    allowVolumeExpansion: true
    parameters: ext4 "1" "true" storageos-api storageos

⚠️ The Ondat API manager periodically syncs labels from Kubernetes PVCs to the corresponding Ondat volume. Therefore changes to Ondat volume labels should be made to the corresponding Kubernetes PVC rather than to the Ondat volume directly.

Ondat Pod labels

Feature Label Values Description
Pod fencing true / false Targets a pod to be fenced in case of node failure. The default value is false

⚠️ For a pod to be fenced by Ondat, a few requirements described in the Fencing Operations page need to be fulfilled.

kubectl label pod $POD

It is recommended to define the fenced label in the pod’s manifest, i.e in the Statefulset definitions. Statefulsets pass labels to their VolumeClaimTemplates. You must set the label only at the spec.template.metadata.labels. Otherwise, the Ondat volumes will fail to provision as only special accepted labels can be passed to volumes.

apiVersion: apps/v1
kind: StatefulSet
  name: my-statefulset
    matchLabels: # <----- Note that the matchLabels don't have the fenced label
      env: prod
  serviceName: my-statefulset-svc
  replicas: 1
      labels:   # <----- Note that the fenced label IS PRESENT
        env: prod "true"