Persistent storage using VMware vSphere volumes

OKD allows use of VMware vSphere’s Virtual Machine Disk (VMDK) volumes. You can provision your OKD cluster with persistent storage using VMware vSphere. Some familiarity with Kubernetes and VMware vSphere is assumed.

VMware vSphere volumes can be provisioned dynamically. OKD creates the disk in vSphere and attaches this disk to the correct image.

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.

Persistent volumes are not bound to a single project or namespace; they can be shared across the OKD cluster. Persistent volume claims are specific to a project or namespace and can be requested by users.

Additional resources

• VMware vSphere

Dynamically provisioning VMware vSphere volumes

Dynamically provisioning VMware vSphere volumes is the recommended method.

Prerequisites

• An OKD cluster installed on a VMware vSphere version that meets the requirements for the components that you use. See Installing a cluster on vSphere for information about vSphere version support.

You can use either of the following procedures to dynamically provision these volumes using the default storage class.

Dynamically provisioning VMware vSphere volumes using the UI

OKD installs a default storage class, named thin, that uses the thin disk format for provisioning volumes.

Prerequisites

• Storage must exist in the underlying infrastructure before it can be mounted as a volume in OKD.

Procedure

1. In the OKD console, click Storage → Persistent Volume Claims.

2. In the persistent volume claims overview, click Create Persistent Volume Claim.

3. Define the required options on the resulting page.

   1. Select the thin storage class.

   2. Enter a unique name for the storage claim.

   3. Select the access mode to determine the read and write access for the created storage claim.

   4. Define the size of the storage claim.

4. Click Create to create the persistent volume claim and generate a persistent volume.

Dynamically provisioning VMware vSphere volumes using the CLI

OKD installs a default StorageClass, named thin, that uses the thin disk format for provisioning volumes.

Prerequisites

• Storage must exist in the underlying infrastructure before it can be mounted as a volume in OKD.

Procedure (CLI)

1. You can define a VMware vSphere PersistentVolumeClaim by creating a file, pvc.yaml, with the following contents:

   kind: PersistentVolumeClaim
   apiVersion: v1
   metadata:
     name: pvc (1)
   spec:
     accessModes:
     - ReadWriteOnce (2)
     resources:
       requests:
         storage: 1Gi (3)

   1	A unique name that represents the persistent volume claim.
   2	The access mode of the persistent volume claim. With ReadWriteOnce, the volume can be mounted with read and write permissions by a single node.
   3	The size of the persistent volume claim.

2. Create the PersistentVolumeClaim object from the file:

   $ oc create -f pvc.yaml

Statically provisioning VMware vSphere volumes

To statically provision VMware vSphere volumes you must create the virtual machine disks for reference by the persistent volume framework.

Prerequisites

• Storage must exist in the underlying infrastructure before it can be mounted as a volume in OKD.

Procedure

1. Create the virtual machine disks. Virtual machine disks (VMDKs) must be created manually before statically provisioning VMware vSphere volumes. Use either of the following methods:

   • Create using vmkfstools. Access ESX through Secure Shell (SSH) and then use following command to create a VMDK volume:

     $ vmkfstools -c <size> /vmfs/volumes/<datastore-name>/volumes/<disk-name>.vmdk

   • Create using vmware-diskmanager:

     $ shell vmware-vdiskmanager -c -t 0 -s <size> -a lsilogic <disk-name>.vmdk

2. Create a persistent volume that references the VMDKs. Create a file, pv1.yaml, with the PersistentVolume object definition:

   apiVersion: v1
   kind: PersistentVolume
   metadata:
     name: pv1 (1)
   spec:
     capacity:
       storage: 1Gi (2)
     accessModes:
       - ReadWriteOnce
     persistentVolumeReclaimPolicy: Retain
     vsphereVolume: (3)
       volumePath: "[datastore1] volumes/myDisk"  (4)
       fsType: ext4  (5)

   1	The name of the volume. This name is how it is identified by persistent volume claims or pods.
   2	The amount of storage allocated to this volume.
   3	The volume type used, with vsphereVolume for vSphere volumes. The label is used to mount a vSphere VMDK volume into pods. The contents of a volume are preserved when it is unmounted. The volume type supports VMFS and VSAN datastore.
   4	The existing VMDK volume to use. If you used vmkfstools, you must enclose the datastore name in square brackets, [], in the volume definition, as shown previously.
   5	The file system type to mount. For example, ext4, xfs, or other file systems.

   Changing the value of the fsType parameter after the volume is formatted and provisioned can result in data loss and pod failure.

3. Create the PersistentVolume object from the file:

   $ oc create -f pv1.yaml

4. Create a persistent volume claim that maps to the persistent volume you created in the previous step. Create a file, pvc1.yaml, with the PersistentVolumeClaim object definition:

   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: pvc1 (1)
   spec:
     accessModes:
       - ReadWriteOnce (2)
     resources:
      requests:
        storage: "1Gi" (3)
     volumeName: pv1 (4)

   1	A unique name that represents the persistent volume claim.
   2	The access mode of the persistent volume claim. With ReadWriteOnce, the volume can be mounted with read and write permissions by a single node.
   3	The size of the persistent volume claim.
   4	The name of the existing persistent volume.

5. Create the PersistentVolumeClaim object from the file:

   $ oc create -f pvc1.yaml

Formatting VMware vSphere volumes

Before OKD mounts the volume and passes it to a container, it checks that the volume contains a file system that is specified by the fsType parameter value in the PersistentVolume (PV) 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 specified file system.

Because OKD formats them before the first use, you can use unformatted vSphere volumes as PVs.