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Persistent Storage.md

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Persistent Storage

There are many options for providing persistent storage to your Kubernetes cluster. We will cover a simple option of create a single NFS server, which will provide all storage needs for your cluster.

Create an NFS server

Because NFS protocol is not secured, you have to connect to it via a private network. Make sure all your worker nodes which will access the NFS server have access to the private network by setting the privateNetworkName field in the worker node template (as described in Create a Kubernetes Cluster).

Use Kamatera console to create a new NFS service with the following configuration:

  • datacenter: same as worker nodes datacenter
  • image: nfsserver-ubuntuserver-20.04
  • cpu: 1 core
  • ram: 2GB
  • disk size: single disk, as much storage size as needed
  • network interfaces:
    • public network - must have a public network so that the server will have access to the internal and external IP for SSH
    • private network - the same network as the worker nodes private network

Add NFS Storage Class

A storage class allows to dynamically provision storage for Kubernetes workloads. The NFS Subdir External Provisioner project handles provisioning of storage to an NFS server.

Cluster explorer -> kubectl shell

Run the following in the kubectl shell to install the provisioner, replace NFS_SERVER_INTERNAL_IP with the internal IP of the NFS server:

helm repo add nfs-subdir-external-provisioner https://kubernetes-sigs.github.io/nfs-subdir-external-provisioner/ &&\
helm install nfs-subdir-external-provisioner nfs-subdir-external-provisioner/nfs-subdir-external-provisioner \
    --set nfs.server=NFS_SERVER_INTERNAL_IP --set nfs.path=/storage

You can check deployment progress by checking the nfs-subdir-external-provisioner deployment workload.

You can now see the storage class in cluster explorer -> storage -> storage classes.

You should see an nfs-client storage class, you should set it as the default storage class.

Use the storage class from a workload

Edit the nginx workload we created in Accessing Workloads Externally

  • Storage
    • Add volume - create persistent volume claim
      • use a storage class, storage class: nfs-client
      • access mode: choose any access mode you want
      • capacity: input required capacity (it is not actually allocated in the NFS server, so it doesn't matter what value you use)
      • mount point: /usr/share/nginx/html

When you access the nginx workload via HTTP you should now get a 403 Forbidden error because the storage does not contain any files for ngins to serve.

SSH to the nfs server

All the provisioned paths will be under /storage directory, check the provisioned directory:

ls /storage/

You should see a directory like default-test-pvc-858c2c43-1987-4619-9542-efdbb9658d71

Change to that directory

cd /storage/default-test-pvc-858c2c43-1987-4619-9542-efdbb9658d71

Create an index.html file:

echo Hello World > index.html

You should now see Hello World when accessing the Nginx workload

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