Using Storage

KD clusters with storage

Some of the YAML file basenames in the deploy/example_clusters/ have a -stor suffix. This is just a convention used among these example files to indicate that the virtual cluster spec requests persistent storage. Several of the examples have both persistent and non-persistent variants.

Note that if you are using persistent storage, you may wish to create a KubeDirectorConfig object (as described in the next section configuring KD), for declaring a specific defaultStorageClassName value.

Alternately, you can declare a storageClassName in the persistent storage spec section of each virtual cluster spec. If no storage class value is declared in either the KubeDirectorConfig or the virtual cluster, then the K8s default storage class will be used.

Explore lab environment

Let's explore the lab environment, first StorageClasses:

$ kubectl get storageclass
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
standard (default) k8s.io/minikube-hostpath Delete Immediate false 11d

Next check if that are any PersistentVolumes:

$ kubectl get pv
No resources found

Finally, check for PersistentVolumeClaims:

$ kubectl get pvc
No resources found in default namespace.

Deploy a cluster with default storage

We will deploy a ubuntu18.04 cluster with storage.

First we will change the configuration to support our lab environment.

  • Edit deploy/example_clusters/cr-cluster-ubuntu18.04-stor.yaml
    • change both instances of memory: "4Gi" to memory: "1Gi"
    • change both instances of CPU: "2" to CPU: "1"

Now deploy the cluster:

$ kubectl apply -f deploy/example_clusters/cr-cluster-ubuntu18.04-stor.yaml
kubedirectorcluster.kubedirector.hpe.com/ubuntu18.04-persistent created

Let's take a look at the PersistentVolumes:

$ kubectl get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-586fc6ec-6106-40b4-af06-1084b384e23f 40Gi RWO Delete Bound default/p-kdss-s4cqf-0 standard 4m58s

If we describe the pv created for our Ubuntu 18.04 instance, we can find the storage location:

kubectl describe pv pvc-586fc6ec-6106-40b4-af06-1084b384e23f
...
Source:
Type: HostPath (bare host directory volume)
Path: /tmp/hostpath-provisioner/p-kdss-s4cqf-0
HostPathType:
...

Finally, we can check the host folder contents:

$ ls -l /tmp/hostpath-provisioner/p-kdss-s4cqf-0/
total 8
drwxr-xr-x 69 root root 4096 Sep 16 11:34 etc
drwxr-xr-x 3 root root 22 Jul 16 11:15 home

We can see that the cluster's etc and home folders are persistent.

Deploy a cluster with custom storage

You can declare a storageClassName in the persistent storage spec section of each virtual cluster spec.

Here is the spec for deploy/example_clusters/cr-cluster-ubuntu18.04-stor.yaml:

apiVersion: "kubedirector.hpe.com/v1beta1"
kind: "KubeDirectorCluster"
metadata:
name: "ubuntu18.04-persistent"
spec:
app: ubuntu18x
roles:
- id: vanilla_ubuntu
members: 1
resources:
requests:
memory: "1Gi"
cpu: "1"
limits:
memory: "1Gi"
cpu: "1"
storage:
size: "40Gi"

The KubeDirectorCluster spec has a definition for PersistentStorageSpec. Inside that element, are the fields size and storageClassName.

It would appear that we can modify deploy/example_clusters/cr-cluster-ubuntu18.04-stor.yaml to add the storageClassName as follows:

apiVersion: "kubedirector.hpe.com/v1beta1"
kind: "KubeDirectorCluster"
metadata:
name: "ubuntu18.04-persistent"
spec:
app: ubuntu18x
roles:
- id: vanilla_ubuntu
members: 1
resources:
requests:
memory: "1Gi"
cpu: "1"
limits:
memory: "1Gi"
cpu: "1"
storage:
size: "40Gi"
storageClassName: "yourStorageClassName"
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