[SHORT] Extending Kubernetes StatefulSet PVC Without Downtime

Kubernetes troubleshooting series

Problem

In Kubernetes, the size of a Persistent Volume Claim (PVC) cannot be directly updated for a Statefulset object. This limitation exists because the PVC is bound to a Persistent Volume (PV) that has a fixed capacity.

When you create a PVC for a StatefulSet, it requests a specific amount of storage capacity. This request is fulfilled by binding the PVC to an available PV that meets the capacity requirement. Once the PVC is bound to a PV, the capacity cannot be changed because it would require modifying the underlying storage resource.

Solution

To extend the size of a PVC in a StatefulSet, you generally need to follow these steps:

1. Update the PVC object

Make sure that your StorageClass has ALLOWVOLUMEEXPANSION=true property

$ kubectl edit pvc  # Change "storage" from both places

$ kubectl describe pvc  # Now when you describe your PVC you should see the changes

2. Delete the StatefulSet object

$ kubectl delete sts --cascade=orphan  # Use the flag --cascade=orphan to delete the StatefulSet and keep its pods running

3. Update the StatefulSet manifest and redeploy it

$ kubectl apply -f sts.yaml # Before applying you need to change the "storage" size as well in sts.yaml file
$ kubectl rollout restart sts  # Restart the pods one at a time, the pod's PVC will be extended during the restart

Thanks for reading. I hope this short story was helpful. If you are interested, check out my other Medium articles.

👋 If you find this helpful, please click the clap 👏 button below a few times to show your support for the author 👇

🚀Join FAUN Developer Community & Get Similar Stories in your Inbox Each Week

[SHORT] Extending Kubernetes Statefulset Pvc was originally published in FAUN — Developer Community 🐾 on Medium, where people are continuing the conversation by highlighting and responding to this story.