Kubernetes Changed Block Tracking API - Beta Differences

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Kubernetes Changed Block Tracking API - Beta DifferencesBy Prasad Ghangal (Veeam Kasten) |
Monday, September 14, 2026Changed Block Tracking (CBT) support for CSI drivers
shipped as Alpha in
September 2025. With the March 2026 v1.0.0 release of the
external-snapshot-metadata
project, the feature moved to Beta.If you aren't yet familiar with changed block tracking for storage in
Kubernetes, the
Alpha announcement covers
the motivation, the three primary components (the CSI SnapshotMetadata
gRPC service, the SnapshotMetadataService CRD, and the
external-snapshot-metadata sidecar), and a walkthrough of how to use the
API. CBT currently applies to block volumes; file-volume and network
file-share changed-list tracking is not covered by this feature. This post
focuses on what is different in Beta.What's new in BetaThe main change in that release was the promotion of the
SnapshotMetadataService CRD from v1alpha1 to v1beta1. The CRD used to
advertise a driver's metadata service now serves
cbt.storage.k8s.io/v1beta1. The schema itself is unchanged, but this
release removed v1alpha1 (rather than serving it alongside the new version).
If you are upgrading from Alpha, you need to:Re-apply the CRD definition shipped with v1.0.0.Update SnapshotMetadataService manifests to use
apiVersion: cbt.storage.k8s.io/v1beta1.Update any client or controller code that talks to the CRD.This is a one-time change. There is no automatic conversion between the two
versions.CompatibilityMinimum Kubernetes version: 1.33CSI spec: 1.10 or newerContainer image: registry.k8s.io/sig-storage/csi-snapshot-metadata:v1.0.0Trying it outThe Getting Started section in the Alpha
blog still
applies. In short:Make sure your CSI driver supports volume snapshots and ships the
external-snapshot-metadata sidecar.Install the SnapshotMetadataService CRD (the v1beta1 definition from
the v1.0.0 release).Create a SnapshotMetadataService resource for your driver.Use a client — snapshot-metadata-lister, or your own implementation —
to call GetMetadataAllocated and GetMetadataDelta.If you want to see the full flow end-to-end, the
hostpath driver example
is a good starting point.What's next?The focus for the rest of the Beta cycle is wider CSI driver adoption and
operational feedback before the feature moves towards GA. If you maintain a
CSI driver, this is a good time to evaluate adding support. If you are
building a backup application on top of the API, feedback on the streaming
clients and the iterator package is very welcome.Where can I learn more?The CSI developer
documentation
for snapshot metadata.KEP-3314.The
external-snapshot-metadata
repository.The gRPC
schema.The
snapshot-metadata-lister
example client.How do I get involved?This work is the result of contributions from many people across SIG Storage.
A big thank you to everyone who helped review, code, and test the feature
through Alpha and into Beta:Ben Swartzlander (bswartz)Carl Braganza (carlbraganza)Daniil Fedotov (hairyhum)Ivan Sim (ihcsim)Nikhil Ladha (Nikhil-Ladha)Praveen M (iPraveenParihar)Rakshith R (Rakshith-R)Xing Yang (xing-yang)If you would like to get involved with CSI or storage in Kubernetes,
SIG Storage
is the place to start. The Data Protection Working
Group
also holds regular meetings, and new attendees are always welcome.←PreviousNext→Last modified September 04, 2026 at 9:58 PM PST: blog: schedule CSI changed block tracking article for 2026-09-14 (a25236f908)