Change GKE storage class without losing content

Question

I've inherited a terraform/helm based GKE with a set of deployments and services in production environment. All of them use the default storage class as PVC.

I would like to switch to a more robust way of storage (default retain or even Filestore+NFS). I was wondering if there is a way to switch the storage class to the newer ones without loosing or manually move the content from the oldest default volumes. This eventually using terraform and updating the Helm charts for consistency.

Is there a way to do so?

Answer 1

You cannot change your StorageClass to a different one and expect the data to not be lost.

Think about your StorageClass as a way to tell Kubernetes what are the available storage options for use. You could have a NFS storage and Ceph storage. Changing the StorageClass for a PVC that stores your data will not transfer the data to a new location.

You won't be even able to change most of the parameters in already created StorageClasses and PVC's.

You can read more about it by following below links:

• Kubernetes.io: Storage classes
• Cloud.google.com: Kubernetes Engine: How to: Persistent Volumes: ssd-pd
• Stackoverflow.com: How do I change the storage class of existing persistent volumes?
• Cloud.google.com: Compute: Disks: Create snapshots - for your disks backup

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I was wondering if there is a way to switch the storage class to the newer ones without loosing (the data I assume)

As said previously it's not possible to just change the StorageClass to a different one.

or manually move the content from the oldest default volumes.

Yes, this is possible and there are several ways to do it. The exact situation you are facing is unknown to us (what exact resources are you having, the data on it, the way they are deployed etc.).

Please take a look on below resources:

• Medium.com: Migrate Kubernetes volume data - you could use this guide to mount old volume and a new one (Filestore PVC?) to copy the contents of old volume to a new one.
• Cloud.google.com: Filestore: Accessing fileshares - this is the guide to create PVC from Filestore.
• Velero.io

You can use above example with copying files between PVC's to create a Job that will do it automatically.

This eventually using terraform and updating the helm charts for consistency.

If you mean to create your resources supporting new storage you configured, it's possible. You will need to modify your existing resources/create new resources to support new storages. Please make sure you tested your solution before using it on production.