Kubernetes Changed Block Tracking API Promotes to Beta, Requires Manual Upgrade

CBT API Reaches Beta Status

The Changed Block Tracking (CBT) API for Kubernetes, which provides support for CSI drivers, has transitioned from Alpha to Beta. This milestone was achieved with the March 2026 v1.0.0 release of the external-snapshot-metadata project. The CBT API currently supports block volumes, with file-volume and network file-share tracking not included in this feature.

Key Changes in Beta Release

The primary change in the Beta release is the promotion of the SnapshotMetadataService CRD from v1alpha1 to v1beta1. This means the CRD now serves cbt.storage.k8s.io/v1beta1. The schema of the CRD remains unchanged, but the v1alpha1 version has been removed, not served alongside the new version.

Upgrade Requirements for Alpha Users

Users upgrading from the Alpha version must re-apply the CRD definition from v1.0.0, update SnapshotMetadataService manifests to use apiVersion: cbt.storage.k8s.io/v1beta1, and update any client or controller code interacting with the CRD. This is a one-time manual change, as there is no automatic conversion between the two versions. The minimum Kubernetes version required is 1.33, and CSI spec 1.10 or newer is needed.

Next Steps for Beta Cycle

The focus for the remainder of the Beta cycle is to encourage wider CSI driver adoption and gather operational feedback. This feedback will inform further development as the feature progresses towards General Availability (GA). CSI driver maintainers are encouraged to evaluate adding support for the CBT API.