Persistent Storage Using GCE Persistent Disk
Before creating persistent volumes using GCE, OKD must first be properly configured for GCE Persistent Disk.
The Kubernetes persistent volume framework allows administrators to provision a cluster with persistent storage and gives users a way to request those resources without having any knowledge of the underlying infrastructure. GCE Persistent Disk volumes can be provisioned dynamically. Persistent volumes are not bound to a single project or namespace; they can be shared across the OKD cluster. Persistent volume claims, however, are specific to a project or namespace and can be requested by users.
High-availability of storage in the infrastructure is left to the underlying storage provider.
Storage must exist in the underlying infrastructure before it can be mounted as a volume in OKD. After ensuring OKD is configured for GCE PersistentDisk, all that is required for OKD and GCE is an GCE Persistent Disk volume ID and the
You must define your persistent volume in an object definition before creating it in OKD:
apiVersion: "v1" kind: "PersistentVolume" metadata: name: "pv0001" (1) spec: capacity: storage: "5Gi" (2) accessModes: - "ReadWriteOnce" gcePersistentDisk: (3) fsType: "ext4" (4) pdName: "pd-disk-1" (5)
|1||The name of the volume. This will be how it is identified via persistent volume claims or from pods.|
|2||The amount of storage allocated to this volume.|
|3||This defines the volume type being used, in this case the gcePersistentDisk plug-in.|
|4||File system type to mount.|
|5||This is the GCE Persistent Disk volume that will be used.|
Changing the value of the
Save your definition to a file, for example gce-pv.yaml, and create the persistent volume:
# oc create -f gce-pv.yaml persistentvolume "pv0001" created
Verify that the persistent volume was created:
# oc get pv NAME LABELS CAPACITY ACCESSMODES STATUS CLAIM REASON AGE pv0001 <none> 5Gi RWO Available 2s
Users can then request storage using persistent volume claims, which can now utilize your new persistent volume.
Persistent volume claims only exist in the user’s namespace and can only be referenced by a pod within that same namespace. Any attempt to access a persistent volume from a different namespace causes the pod to fail.
Before OKD mounts the volume and passes it to a container, it checks that it contains a file system as specified by the
fsType parameter in the persistent volume definition. If the device is not formatted with the file system, all data from the device is erased and the device is automatically formatted with the given file system.
This allows using unformatted GCE volumes as persistent volumes, because OKD formats them before the first use.