In-tree storage drivers that are traditionally shipped with OKD are being deprecated and replaced by their equivalent Container Storage Interface (CSI) drivers. OKD provides automatic migration for certain supported in-tree volume plug-ins to their equivalent CSI drivers.
Volumes that are provisioned by using in-tree storage plug-ins, and that are supported by this feature, are migrated to their counterpart Container Storage Interface (CSI) drivers. This process does not perform any data migration; OKD only translates the persistent volume object in memory. As a result, the translated persistent volume object is not stored on disk, nor is its contents changed.
The following in-tree to CSI drivers are supported:
|In-tree/CSI drivers||Support level||CSI auto migration enabled automatically?|
Generally available (GA)
Yes. For more information, see "Automatic migration of in-tree volumes to CSI".
Techology Preview (TP)
No. To enable, see "Manually enabling CSI automatic migration".
CSI automatic migration should be seamless. This feature does not change how you use all existing API objects: for example,
Enabling CSI automatic migration for in-tree persistent volumes (PVs) or persistent volume claims (PVCs) does not enable any new CSI driver features, such as snapshots or expansion, if the original in-tree storage plug-in did not support it.
OKD supports automatic and seamless migration for the following in-tree volume types to their Container Storage Interface (CSI) driver counterpart:
CSI migration for these volume types is considered generally available (GA), and requires no manual intervention.
For new OKD 4.11, and later, installations, the default storage class is the CSI storage class. All volumes provisioned using this storage class are CSI persistent volumes (PVs).
For clusters upgraded from 4.10, and earlier, to 4.11, and later, the CSI storage class is created, and is set as the default if no default storage class was set prior to the upgrade. In the very unlikely case that there is a storage class with the same name, the existing storage class remains unchanged. Any existing in-tree storage classes remain, and might be necessary for certain features, such as volume expansion to work for existing in-tree PVs. While storage class referencing to the in-tree storage plug-in will continue working, we recommend that you switch the default storage class to the CSI storage class.
If you want to test Container Storage Interface (CSI) migration in development or staging OKD clusters, you must manually enable in-tree to CSI migration for the following in-tree volume types:
AWS Elastic Block Storage (EBS)
Google Compute Engine Persistent Disk (GCE-PD)
VMware vSphere Disk
CSI automatic migration for the preceding in-tree volume plug-ins and CSI driver pairs is 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/.
After migration, the default storage class remains the in-tree storage class.
CSI automatic migration will be enabled by default for all storage in-tree plug-ins in a future OKD release, so it is highly recommended that you test it now and report any issues.
Enabling CSI automatic migration drains, and then restarts, all nodes in the cluster in sequence. This might take some time.
Enable feature gates (see Nodes → Enabling features using feature gates).
After turning on Technology Preview features using feature gates, they cannot be turned off. As a result, cluster upgrades are prevented.
The following configuration example enables CSI automatic migration for all CSI drivers supported by this feature that are currently in Technology Preview (TP) status:
apiVersion: config.openshift.io/v1 kind: FeatureGate metadata: name: cluster spec: featureSet: TechPreviewNoUpgrade (1) ...
|1||Enables automatic migration for AWS EBS, GCP, Azure File, and VMware vSphere.|
You can specify CSI automatic migration for a selected CSI driver by setting
featureSet and for
featuregates to one of the following:
The following configuration example enables automatic migration to the AWS EBS CSI driver only:
apiVersion: config.openshift.io/v1 kind: FeatureGate metadata: name: cluster spec: featureSet: CustomNoUpgrade customNoUpgrade: enabled: - CSIMigrationAWS (1) ...
|1||Enables automatic migration for AWS EBS only.|