If you are not familiar with the oc command, refer to OpenShift - Getting Started with the oc command.

A persistent volume (PV) is the "physical" volume (such as a hard disk drive or solid state drive) on the host machine (node) that stores your persistent data, whereas a persistent volume claim (PVC) is a reference to a persistent volume, used by a pod.

The oc get pvc command will return the list of persistent volume claims. Access Modes can be one or more of the following:

• ReadWriteOnce (RWO) - The volume may only be mounted on a single node
• ReadWriteOncePod (RWOP) - The volume may only be mounted on a single pod
• ReadOnlyMany (ROX) - The volume may be mounted on different nodes
• ReadWriteMany (RWX) - The volume can be mounted on different nodes

~]$ oc get pvc
NAME          STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
my-pvc-1      Bound    pvc-385996a0-70af-4791-aa8e-9e6459e6b123   1Gi        RWO            file-storage   659d
my-pvc-2      Bound    pvc-8aeddd4d-aad5-4039-8d04-640a71c9a72d   10Gi       RWO            file-storage   659d
my-pvc-3      Bound    pvc-0050144d-940c-4c4e-a23a-2a660a5490eb   10Gi       RWO            file-storage   659d

The oc describe pvc command can be used to display the details of a Persistent Volume Claim. In this example, the details of the pvc001 Persistent Volume Claim will be displayed. Notice in this example that the Persistent Volume Claim is being used by the pod "my-app-2mp2k".

~]$ oc describe pvc my-pvc-1
Name:          my-pvc-1
Namespace:     foo
StorageClass:  file-storage
Status:        Bound
Volume:        pvc-2db07c57-e282-48e7-bfb1-4cbd7245c25e
Labels:        <none>
Annotations:   pv.kubernetes.io/bind-completed: yes
               pv.kubernetes.io/bound-by-controller: yes
               volume.beta.kubernetes.io/storage-provisioner: csi.trident.netapp.io
Finalizers:    [kubernetes.io/pvc-protection]
Capacity:      1Gi
Access Modes:  RWO
VolumeMode:    Filesystem
Used By:       my-app-2mp2k

The oc describe pod command can be used to see that the Persistent Volume Claim is mounted to the /var/data directory in the container.

~]$ oc describe pod my-app-2mp2k
Containers:
  my-container:
    Mounts:
      /var/data from my-pvc-1 (rw)

The oc exec and df command can be used to get the amount of storage being used by the /var/data mount in the container.

~]$ oc exec pod/my-app-2mp2k -- df
Filesystem                                                                                    1K-blocks     Used Available Use% Mounted on
overlay                                                                                       125277164 46024772  79252392  37% /
tmpfs                                                                                             65536        0     65536   0% /dev
tmpfs                                                                                          12333448        0  12333448   0% /sys/fs/cgroup
shm                                                                                               65536        0     65536   0% /dev/shm
tmpfs                                                                                          12333448    63876  12269572   1% /etc/hostname
10.84.234.142:/trident_qtree_pool_k8s_LDKEDEQUWG/k8s_pvc-2db07c57-e282-48e7-bfb1-4cbd7245c25e 125277164 46024772  79252392  37% /var/data                                                        
tmpfs                                                                                          12333448       32  12333416   1% /run/secrets/kubernetes.io/serviceaccount
tmpfs                                                                                          12333448        0  12333448   0% /proc/acpi
tmpfs                                                                                          12333448        0  12333448   0% /proc/scsi
tmpfs                                                                                          12333448        0  12333448   0% /sys/firmware