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Using Block Storage

PFCP supports block storage as PersistentVolume resources with either ReadWriteOnce or ReadWriteOncePod access modes. For ReadWriteOncePod volumes, access is restricted to a single pod only.

Creating and Mounting a Filesystem from PersistentVolumeClaim to a Pod

To utilize block storage by creating a filesystem on it, you should first create a PersistentVolumeClaim resource to request the necessary storage capacity, then mount the dynamically provisioned PersistentVolume from within your pod. Below is an example demonstrating this process.

1. Create a PersistentVolumeClaim by specifying the organization-specific StorageClass. The available StorageClass name is standard-rwo-<organization-name>.

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: hello-sample-pvc
   spec:
     accessModes:
     - ReadWriteOnce
     resources:
       requests:
         storage: 10Gi
     storageClassName: standard-rwo-<organization-name>
     volumeMode: Filesystem
   

   In this example, we’re creating a PersistentVolumeClaim to request a filesystem on 10GiB of block storage. Since volumeMode defaults to Filesystem, this specification is technically optional—the resulting volume would be created identically without this explicit declaration. After applying this manifest to Kubernetes, the PersistentVolume will be created dynamically, and you can verify that the PersistentVolumeClaim status becomes Bound as follows:

   $ kubectl -n org-<organization-name> get pvc
   NAME               STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS           VOLUMEATTRIBUTESCLASS   AGE
   hello-sample-pvc   Bound    pvc-ac98a6ff-58cd-4bef-8057-4837949107d0   10Gi       RWO            standard-rwo-<organization-name>   <unset>                 7s
   

2. By specifying this PersistentVolumeClaim in your pod configuration, you can mount it and use it as file storage.

   apiVersion: v1
   kind: Pod
   metadata:
     name: jupyter-notebook
   spec:
     containers:
     - name: jupyter-notebook
       image: quay.io/jupyter/scipy-notebook:2024-03-14
       volumeMounts:
       - mountPath: "/hello-sample"
         name: hello-sample-pv
     volumes:
     - name: hello-sample-pv
       persistentVolumeClaim:
         claimName: hello-sample-pvc
   

Using Block Storage Directly from a Pod Without Creating a Filesystem

To use block storage directly as a raw block device, you should create a PersistentVolumeClaim to request the necessary storage capacity, then access the dynamically provisioned PersistentVolume through your pod via a device file. Below is an example demonstrating this approach.

1. Create a PersistentVolumeClaim by specifying the organization-specific StorageClass. The available StorageClass name is standard-rwo-<organization-name>.

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: hello-sample-pvc
   spec:
     accessModes:
     - ReadWriteOnce
     resources:
       requests:
         storage: 10Gi
     storageClassName: standard-rwo-<organization-name>
     volumeMode: Block
   

   In this example, we’re creating a PersistentVolumeClaim to use 10GiB of block storage as a raw block device. By specifying Block as the volumeMode, we prevent any filesystem creation operations on the block storage. After applying this manifest to Kubernetes, the PersistentVolume will be created dynamically, and you can verify that the PersistentVolumeClaim status becomes Bound as follows:

   $ kubectl -n org-<organization-name> get pvc
   NAME               STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS           VOLUMEATTRIBUTESCLASS   AGE
   hello-sample-pvc   Bound    pvc-fb34c017-ce51-488c-a445-65981b031e0b   10Gi       RWO            standard-rwo-<organization-name>   <unset>                 119s
   

2. By specifying this PersistentVolumeClaim in your pod configuration as a device file, you can access it directly as a block device from within your pod.

   apiVersion: v1
   kind: Pod
   metadata:
     name: block-demo
   spec:
     containers:
     - name: block-demo
       image: ubuntu
       command:
       - sleep
       - "3600"
       volumeDevices:
       - name: hello-sample-pv
         devicePath: /dev/block
     volumes:
     - name: hello-sample-pv
       persistentVolumeClaim:
         claimName: hello-sample-pvc
   

   This example demonstrates how to operate the block device from within the pod. Here, the device file is mapped to nvme2n1, and you can confirm it is recognized as a block device with the specified 10GiB capacity from the PersistentVolumeClaim.

   $ kubectl -n org-<organization-name> exec -it block-demo -- bash
   root@block-demo:/# ls -lF /dev/block
   brw-rw---- 1 root disk 259, 20 Aug  9 03:49 /dev/block
   root@block-demo:/# lsblk /dev/block
   NAME    MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
   nvme2n1 259:20   0  10G  0 disk
   root@block-demo:/#
   

References

• Persistent Volumes | Kubernetes