Kubernetes v1.37 Enables Storage Version Migration by Default

Storage Version Migration Reaches GA

Kubernetes v1.37 officially includes Storage Version Migration (SVM) as a generally available feature. This means the built-in StorageVersionMigration API (storagemigration.k8s.io/v1) and its control plane controller are now stable and active by default in all Kubernetes v1.37 clusters.

Addressing Storage Version Inconsistencies

Kubernetes stores API resources using specific storage versions. When the schema for a resource changes, existing resources may remain stored in older versions. This creates problems when deprecating older API versions of Custom Resource Definitions (CRDs), such as moving from v1alpha1 to v1, or when implementing encryption at rest and rotating encryption keys. Resources stored in older versions or with old encryption keys are not automatically updated.

Previous Migration Challenges

Historically, cluster administrators and CRD authors had to manually update resources. This involved using kubectl get/replace scripts or deploying the out-of-tree kube-storage-version-migrator component. These methods were often time-consuming, prone to errors, and lacked proper monitoring capabilities.

Simplified Migration Process

With SVM, initiating a storage version migration is done by creating a declarative StorageVersionMigration object. The built-in StorageVersionMigrator controller monitors these objects and automatically rewrites existing resources to conform to the default storage version for their respective APIs. This automates a previously manual and complex task.