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.
Pods using raw block volumes must be configured to allow privileged containers.
The following table displays which volume plug-ins support block volumes.
| Volume Plug-in | Manually provisioned | Dynamically provisioned | Fully supported |
|---|---|---|---|
| AWS EBS | ✅ | ✅ | ✅ |
| Azure Disk | ✅ | ✅ | ✅ |
| Azure File | |||
| Cinder | ✅ | ✅ | |
| Fibre Channel | ✅ | ||
| GCP | ✅ | ✅ | ✅ |
| HostPath | |||
| iSCSI | ✅ | ✅ | |
| Local volume | ✅ | ✅ | |
| NFS | |||
| Red Hat OpenShift Container Storage | ✅ | ✅ | ✅ |
| VMware vSphere | ✅ | ✅ | ✅ |
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
volumeModemust be set toBlockto 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
volumeModemust be set toBlockto 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 ofvolumeMounts, is used for block devices. OnlyPersistentVolumeClaimsources can be used with raw block volumes.- 2
devicePath, instead ofmountPath, represents the path to the physical device where the raw block is mapped to the system.- 3
- The volume source must be of type
persistentVolumeClaimand must match the name of the PVC as expected.
| Value | Default |
|---|---|
| Filesystem | Yes |
| Block | No |
PV volumeMode | PVC volumeMode | Binding 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 |
Unspecified values result in the default value of Filesystem.
