2.5. Block volume support

OpenShift Container Platform can statically provision raw block volumes. These volumes do not have a file system, and can provide performance benefits for applications that either write to the disk directly or implement their own storage service.

Raw block volumes are provisioned by specifying volumeMode: Block in the PV and PVC specification.

重要

Pods using raw block volumes must be configured to allow privileged containers.

The following table displays which volume plug-ins support block volumes.

表 2.4. Block volume support

Volume Plug-inManually provisionedDynamically provisionedFully supported

AWS EBS

✅

✅

✅

Azure Disk

✅

✅

✅

Azure File

   

Cinder

✅

✅

 

Fibre Channel

✅

  

GCP

✅

✅

✅

HostPath

   

iSCSI

✅

 

✅

Local volume

✅

 

✅

NFS

   

Red Hat OpenShift Container Storage

✅

✅

✅

VMware vSphere

✅

✅

✅

注意

Any of the block volumes that can be provisioned manually, but are not provided as fully supported, are included as a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see https://access.redhat.com/support/offerings/techpreview/.

2.5.1. Block volume examples

PV example

apiVersion: v1
kind: PersistentVolume
metadata:
  name: block-pv
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  volumeMode: Block 1
  persistentVolumeReclaimPolicy: Retain
  fc:
    targetWWNs: ["50060e801049cfd1"]
    lun: 0
    readOnly: false

1
volumeMode must be set to Block to indicate that this PV is a raw block volume.

PVC example

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: block-pvc
spec:
  accessModes:
    - ReadWriteOnce
  volumeMode: Block 1
  resources:
    requests:
      storage: 10Gi

1
volumeMode must be set to Block to indicate that a raw block PVC is requested.

Pod specification example

apiVersion: v1
kind: Pod
metadata:
  name: pod-with-block-volume
spec:
  containers:
    - name: fc-container
      image: fedora:26
      command: ["/bin/sh", "-c"]
      args: [ "tail -f /dev/null" ]
      volumeDevices:  1
        - name: data
          devicePath: /dev/xvda 2
  volumes:
    - name: data
      persistentVolumeClaim:
        claimName: block-pvc 3

1
volumeDevices, instead of volumeMounts, is used for block devices. Only PersistentVolumeClaim sources can be used with raw block volumes.
2
devicePath, instead of mountPath, represents the path to the physical device where the raw block is mapped to the system.
3
The volume source must be of type persistentVolumeClaim and must match the name of the PVC as expected.

表 2.5. Accepted values for volumeMode

ValueDefault

Filesystem

Yes

Block

No

表 2.6. Binding scenarios for block volumes

PV volumeModePVC volumeModeBinding result

Filesystem

Filesystem

Bind

Unspecified

Unspecified

Bind

Filesystem

Unspecified

Bind

Unspecified

Filesystem

Bind

Block

Block

Bind

Unspecified

Block

No Bind

Block

Unspecified

No Bind

Filesystem

Block

No Bind

Block

Filesystem

No Bind

重要

Unspecified values result in the default value of Filesystem.