Kubernetes - StatefulSet and Storages - multichoice questions

Given a cluster with a running MySQL StatefulSet:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
spec:
  serviceName: "mysql"
  replicas: 3
  selector:
    matchLabels:
      app: mysql
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - name: mysql-container
        image: mysql:latest
        env:
        - name: MYSQL_ROOT_PASSWORD
          value: "your-root-password"
        - name: MYSQL_DATABASE
          value: "your-database-name"
        - name: MYSQL_USER
          value: "your-mysql-user"
        - name: MYSQL_PASSWORD
          value: "your-mysql-password"
        ports:
        - containerPort: 3306
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql

  volumeClaimTemplates:
  - metadata:
      name: mysql-persistent-storage
    spec:
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 5Gi

Answer the below 3 questions.

Question 1

Choose all correct statement(s)

Performing the below command:

kubectl scale statefulset mysql --replicas=2

Will not delete the volume associated with mysql-2 replica.
Will delete the volume associated with mysql-2 replica.
Will delete the PVC associated with mysql-0 replica.
Will not delete the PVC associated with mysql-2 replica.

Question 2

You are told that when the StatefulSet has been deployed for the first time, for some reason, readiness probes of pod mysql-1 were failed.

Choose the correct statement(s) regarding the Pod status and Pod condition of mysql-0 and mysql-2:

Pod mysql-2 status is Pending.
Pod mysql-2 status is Unknown and the Initialized condition is met.
Pod mysql-0 status is Running and the Ready condition is met.
Pod mysql-0 status is Terminating and the Ready condition is met.

Question 3

During RollingUpdate, the StatefulSet controller will delete and recreate each Pod in the StatefulSet, in reverse ordinal order.

Here is the Pod status before the rolling update:

$ kubectl get pod -l app=mysql
NAME        READY     STATUS    RESTARTS   AGE
mysql-0     1/1       Running   0          7m
mysql-1     1/1       Running   0          7m
mysql-2     1/1       Running   0          8m

And during the rolling update (using the -w flag to "watch" the output updates in real-time):

$ kubectl get pod -l app=mysql -w
NAME        READY     STATUS              RESTARTS   AGE
mysql-2     1/1       Terminating         0          8m
mysql-2     1/1       Terminating         0          8m
mysql-2     0/1       Terminating         0          8m
mysql-2     0/1       Terminating         0          8m
mysql-2     0/1       Terminating         0          8m
mysql-2     0/1       Terminating         0          8m
mysql-1     1/1       Terminating         0          0s
mysql-1     0/1       Terminating         0          0s
mysql-1     0/1       Terminating         0          0s
mysql-1     0/1       Terminating         0          19s
mysql-2     0/1       Pending             0          8m
mysql-2     0/1       Pending             0          8m
mysql-2     0/1       ContainerCreating   0          8m
mysql-2     1/1       Running             0          8m
mysql-1     0/1       Pending             0          0s
mysql-1     0/1       Pending             0          0s
mysql-1     0/1       ContainerCreating   0          0s
mysql-1     1/1       Running             0          6s
mysql-0     1/1       Terminating         0          7m
mysql-0     1/1       Terminating         0          7m
mysql-0     0/1       Terminating         0          7m
mysql-0     0/1       Terminating         0          7m
mysql-0     0/1       Terminating         0          7m
mysql-0     0/1       Terminating         0          7m
mysql-0     0/1       Pending             0          0s
mysql-0     0/1       Pending             0          0s
mysql-0     0/1       ContainerCreating   0          0s
mysql-0     1/1       Running             0          10s

What's wrong with the above output?

The output is ok.
The pods should be terminated in a reverse order: mysql-0 first, then mysql-1, and mysql-3 last.
mysql-1 is terminating before mysql-2 is Running.
None of the above.

Question 4

What is the different between a PV and a PVC?

PV is used by Pods, while PVC is used by PersistentVolumeClaims.
PV is dynamically created by Kubernetes, while PVC is statically provisioned by cluster administrators.
PV represents physical storage resources, while PVC is a request for storage resources.
PV is namespace-specific, while PVC is cluster-wide.

Question 5

A StatefulSet uses hostPath for storage. After performing a rolling update, some Pod was scheduled on a different node than it was scheduled originally.

The data on the hostPath is automatically replicated to the new node.
The Pod fails to start on the new node, and the data remains on the original node.
The data on the hostPath is lost since hostPath is specific to the node's local filesystem.
In a StatefulSet, Pods are always scheduled on the same node they were scheduled originally.

Question 6

When a PV is configured with the retain reclaim policy, what happens if the associated PVC is deleted?

Both PV and PVC are deleted, freeing up the storage resources.
PV is retained, and the associated PVC is deleted, leaving the PV intact.
Both PV and PVC are retained, preserving the storage resources.
PV is deleted, and the associated PVC is retained, allowing the PV to be used by another PVC.

Question 7

Can 2 PVCs be bound to the same PV?

No!
Yes!
Only in the PV accessModes is ReadWriteMany.
Only in the PV accessModes is ReadWriteMany and is located in the same namespace of the PVC.

Question 8

Given a PVC:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi

Which is bound to the following PV:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: my-pv
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteOnce

Now consider two Pods:

apiVersion: v1
kind: Pod
metadata:
  name: pod-1
spec:
  containers:
  - name: container-1
    image: nginx:latest
    volumeMounts:
    - name: my-storage
      mountPath: /data
  volumes:
  - name: my-storage
    persistentVolumeClaim:
      claimName: my-pvc
---
apiVersion: v1
kind: Pod
metadata:
  name: pod-2
spec:
  containers:
  - name: container-2
    image: busybox:latest
    command: ["/bin/sh", "-c", "sleep 3600"]
    volumeMounts:
    - name: my-storage
      mountPath: /data  
  volumes:
  - name: my-storage
    persistentVolumeClaim:
      claimName: my-pvc

Choose the correct sentence:

The above example can not work since the two Pods can not use the same PVC.
The above example works.
The above example can work only if the two Pods are scheduled on the same node.
None of the above.