Add openebs tutorial

k8s/openebs-pod.yaml

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+apiVersion: v1
+kind: Pod
+metadata:
+  name: openebs-local-hostpath-pod
+spec:
+  volumes:
+  - name: storage
+    persistentVolumeClaim:
+      claimName: local-hostpath-pvc
+  containers:
+  - name: better
+    image: alpine
+    command:
+       - sh
+       - -c
+       - 'while true; do echo "`date` [`hostname`] Kubernetes is better with PVs." >> /mnt/storage/greet.txt; sleep $(($RANDOM % 5 + 20)); done'
+    volumeMounts:
+    - mountPath: /mnt/storage
+      name: storage

slides/k8s/openebs.md

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+# OpenEBS 
+
+ - OpenEBS is a popular open-source storage solution for Kubernetes
+
+ - Think "Container Attached Storage"
+
+ - Supports a wide range of storage engines:
+   - Jiva: for lighter workloads with basic cloning/snapshotting
+
+   - cStor: based on iSCSI
+
+   - Mayastor: light-weight abstraction layer with nVME and vhost-user support
+
+   - OpenEBS Local PV - for lowest latency local volumes
+
+---
+## Installing OpenEBS with Helm
+
+OpenEBS control plane runs as a set of containers on Kubernetes worker nodes. 
+It can be installed with helm:
+
+.exercise[
+
+  - Install OpenEBS
+```bash  
+    kubectl create ns openebs
+    helm repo add openebs https://openebs.github.io/charts
+    helm repo update
+    helm install openebs openebs/openebs --namespace openebs
+```
+]
+
+---
+
+## Installing OpenEBS with Helm
+
+Let's check the running OpenEBS components:
+
+.exercise[
+
+```bash  
+    kubectl get pod -n openebs
+```
+]
+
+Let's check the new StorageClasses:
+
+.exercise[
+
+```bash  
+    kubectl get sc
+```
+]
+
+---
+
+## Default Storage Classes 
+
+For a simple testing of OpenEBS, you can use the below default storage classes:
+
+ - **openebs-jiva-default** for provisioning Jiva Volume (this uses default pool which means the data replicas are created in the /mnt/openebs_disk directory of the Jiva replica pod)
+
+ - **openebs-hostpath** for provisioning Local PV on hostpath.
+
+ - **openebs-device** for provisioning Local PV on device.
+
+For using real disks, you have to create *cStorPools* or *Jiva* pools or *OpenEBS Local PV* based on the requirement and then create corresponding StorageClasses or use default StorageClasses to use them.
+
+---
+
+## Selecting an OpenEBS Storage Engine
+
+Storage engine is chosen by specifying the annotation `openebs.io/cas-type` in the StorageClass specification. StorageClass defines the provisioner details. Separate provisioners are specified for each CAS engine.
+
+Example for Local PV host path:
+
+```yaml
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: localpv-hostpath-sc
+  annotations:
+    openebs.io/cas-type: local
+    cas.openebs.io/config: |
+      - name: BasePath
+        value: "/var/openebs/local"
+      - name: StorageType
+        value: "hostpath"
+provisioner: openebs.io/local
+```
+
+---
+
+## Exploring the host path StorageClass
+
+.exercise[
+    - Let's look at the OpenEBS Local PV host path StorageClass
+    ```bash
+    kubectl get sc openebs-hostpath -oyaml
+    ``` 
+]
+
+---
+
+##  Create a host path PVC
+
+Let's create a Persistent Volume Claim
+.exercise[
+```bash
+kubectl apply -f - <<EOF
+kind: PersistentVolumeClaim
+apiVersion: v1
+metadata:
+  name: local-hostpath-pvc
+spec:
+  storageClassName: openebs-hostpath
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1G
+EOF
+
+kubectl get pvc
+```
+]
+
+---
+## Create a pod to consume the PV
+
+.exercise[
+- Create a pod from yaml:
+```
+kubectl apply -f ~/container.training/k8s/openebs-pod.yaml
+```
+- Look at the pod definition:
+```
+  volumes:
+  \- name: my-storage
+     persistentVolumeClaim:
+       claimName: local-hostpath-pvc
+  containers:
+....  
+    volumeMounts:
+    \- mountPath: /mnt/storage
+      name: my-storage
+```
+]
+
+---
+### Verify the data is written
+
+.exercise[
+ - Get the worker node where the pod is located
+ ```
+kubectl get pod openebs-local-hostpath-pod -ojsonpath
+="{ .spec.nodeName }"
+```
+- ssh into the node
+
+- check the volume content
+```
+sudo cat /var/openebs/local/pvc-*/greet.txt
+```
+]