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Kubernetes PV Migration from In-tree Spec to CSI

This document outlines the steps required to migrate Kubernetes Persistent Volumes (PVs) from the in-tree storage specification to the Container Storage Interface (CSI) specification using a Python script.

Disclaimer

This migration will cause downtime for the applications using the PVs. Ensure that you have a maintenance window to perform the migration. This script is tested on a limited set of PVs and may require adjustments to work with your specific environment. Always perform a full backup of the cluster before starting the migration process.

Prerequisites

Before proceeding with the migration process, ensure you have the following prerequisites:

  • Access to a Kubernetes cluster
  • Proper permissions to create and modify Persistent Volumes and Persistent Volume Claims
  • Python 3 and PIP are installed on your system
  • Necessary dependencies installed from requirements.txt: pip install -r requirements.txt
  • The full backup of the cluster should be taken before starting the migration process
  • All workloads using the PVs to be migrated should be stopped

Potential Risks

  • Data loss: Ensure that you have a full backup of the cluster before starting the migration process.
  • Issue that PVCs may not be able to bind to the PVs after migration: Ensure that the storage class and CSI driver are compatible with the PVs.

Python Script Usage

The migration process will be facilitated by a Python script migrate-pvs-k8s-api.py. Below is the usage of the script:

python3 scripts/migrate-pvs-k8s-api.py \
  --context <Kubernetes_context> \
  --storage-class-name <storageClassName> \
  [--loglevel <log_level>] \
  [--logs-directory <logs_directory>]

Script Options

  • -c, --context: Specifies the Kubernetes context to use.
  • -s, --storage-class-name: Specifies the Kubernetes storageClassName to migrate.
  • -l, --loglevel: (Optional) Specifies the verbosity of logging (DEBUG, INFO, WARNING, ERROR, CRITICAL). Default is INFO.
  • -d, --logs-directory: (Optional) Specifies the directory where logs will be stored.

Storage Classes migrat

Migration Process

Follow these steps to migrate PVs from the in-tree spec to the CSI one:

  1. Identify PVs: Determine which PVs need to be migrated. PVs using in-tree storage classes are candidates for migration.

  2. Verify CSI Driver Support: Ensure that the CSI driver corresponding to the desired storage class is installed and supported by your Kubernetes cluster.

  3. Run the Migration Script: Execute the provided Python script, specifying the Kubernetes context and the storage class name to migrate. Optionally, adjust the logging level and logs directory as needed.

  4. Review Logs: Check the logs generated by the script for any errors or warnings. Logs may provide insight into the migration process and any issues encountered.

  5. Verify PV Migration: After running the script, verify that PVs have been successfully migrated to the CSI specification. Use kubectl get pv -o yaml <pv_name> to inspect the PVs and ensure they are using the desired storage class.

  6. Testing: Perform testing to ensure that applications utilizing the migrated PVs continue to function as expected. Verify that data integrity is maintained throughout the migration process.

  7. Cleanup: Once migration is confirmed successful, consider cleaning up any unnecessary resources or logs generated during the process.

Conclusion

By following the steps outlined in this document and utilizing the provided Python script, you can efficiently migrate Kubernetes PVs from the in-tree spec to the CSI one, thereby leveraging the benefits of CSI drivers for storage provisioning and management.