Expanding Kubernetes Cluster Capabilities with Shared Storage

Introduction

• Purpose: Show how to add shared storage to a Kubernetes cluster.
• Demo Focus: Connect Synology NAS as an NFS server for persistent volumes.

Why Use Shared Storage?

• Kubernetes primarily provides compute resources, not storage.
• Workloads needing persistent storage require external solutions.
• Persistent volumes allow workloads to store data temporarily and reconnect after restarts or relocations.

Issues with Host Path Volumes

• Single Node Cluster: Simple setup; volumes are directly accessible.
• Multi-Node Cluster Problems:
  • Workload on one node may need to move to another, losing access to local volumes.
  • Scaling workloads can create conflicts due to access permissions (read-write-once limitation).

Solution: Using NFS Provisioner

• NFS (Network File System):
  • Allows multiple workloads to read/write from the same disk.
  • NFS Container Storage Interface (CSI) integrates with Kubernetes for volume provisioning.

Setting Up NFS

NFS Server Options

1. Install NFS on Kubernetes Node:

   • Quick, but not preferred (risk of losing access if the node fails).
   • Easy installation via SSH and MicroK8s instructions.

2. Use a Dedicated NFS Device: (Preferred Method)

   • Example: Synology DS120 used for backups and now as NFS.
   • Steps to enable NFS on Synology NAS:
     • Log in to NAS manager.
     • Create shared folder and set NFS permissions (allow local IPs, squash users to root).
     • Enable NFS in the file services.

Installing NFS CSI Driver

• Follow instructions for installation using Helm chart on MicroK8s site.
• SSH into cluster and run installation commands.

Creating a Storage Class

• A storage class is a set of instructions for volume provisioning in Kubernetes.
• Example name: NFS CSI.
• Parameters:
  • Specify NFS server's IP and name of the share.
  • Consider setting reclaim policy (retain vs. delete) depending on data importance.

Recap of Storage Class Configuration

• Storage class instructs Kubernetes to provision volumes via NFS CSI.
• Binds requested volumes to NFS server, appearing as shared persistent volumes to workloads.
• Apply the storage class configuration using kubectl apply -f <filename>.

Using Persistent Volume Claims (PVCs)

• Create a PVC with read-write-many access mode and link it to the storage class.
• Apply the PVC configuration similarly using kubectl apply -f <filename>.
• Once bound, integrate the PVC into your deployment by specifying it in the volume section.

Conclusion

• Achieving a production-like Kubernetes cluster with separated storage and compute resources.
• Encouragement to like and subscribe for more content.
• Reminder to check out the previous video on setting up the cluster.