Create a PVC from a snapshot in Tanzu

Summary and Key concepts

Summary:

This article explains how to create, manage, and restore snapshots of Portworx volumes in Kubernetes. It covers both automated periodic snapshots and on-demand snapshots using Kubernetes manifests and the Portworx command-line tool pxctl. The document also details how to use snapshots to clone volumes and restore data, with specific instructions for MySQL applications. The recommended method for managing snapshots is through Stork, and the article includes examples for triggering snapshots using annotations and inline specifications. Additionally, it walks through the process of listing snapshots, restoring from snapshots, and using snapshots to provision new PVCs for pods.

Kubernetes Concepts:

• PersistentVolumeClaim (PVC): Used to request dynamic storage in Kubernetes, can be snapshotted and cloned.
• StorageClass: Defines storage parameters, such as snapshot schedules, for PVCs.
• Annotations: Used to trigger on-demand snapshots and manage snapshot-related configurations.
• ClusterRole: Manages permissions across Kubernetes clusters, often edited to manage snapshots.

Portworx Concepts:

• Stork: Portworx’s scheduler extension for managing data, snapshots, and backups in Kubernetes.

• pxctl: Command-line tool used to manage Portworx volumes, snapshots, and other storage-related tasks.

• Portworx Volume Snapshot: A feature that captures point-in-time copies of volumes for data protection or cloning.

This document will show you how to take a snapshot of a volume using Portworx and use that snapshot as the volume for a new pod.

note

The suggested way to manage snapshots on Kuberenetes is now to use Stork. Instructions for using Stork to manage snapshots can be found here

Managing snapshots through kubectl

Taking periodic snapshots on a running POD

When you create the Storage Class, you can specify a snapshot schedule on the volume as specified below:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: portworx-io-priority-high
provisioner: pxd.portworx.com
parameters:
  repl: "1"
  snap_interval:   "24"
  io_priority:  "high"

Creating a snapshot on demand

You can trigger a new snapshot on a running POD by creating a PersistentVolumeClaim.

Using annotations

Portworx uses a special annotation px/snapshot-source-pvc which can be used to identify the name of the source PVC whose snapshot needs to be taken.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  namespace: prod
  name: ns.prod-name.px-snap-1
  annotations:
    volume.beta.kubernetes.io/storage-class: px-sc
    px/snapshot-source-pvc: px-vol-1
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 6Gi

Note the format of the name field - ns.<namespace_of_source_pvc>-name.<name_of_the_snapshot>. The above example takes a snapshot with the name px-snap-1 of the source PVC px-vol-1 in the prod namespace.

You can run the following command to edit your existing Portworx ClusterRole

kubectl edit clusterrole node-get-put-list-role

Clone from a snapshot

You can restore a clone from a snapshot using the following spec file. In 1.3 and higher releases, this is required to create a read-write clone as snapshots are read only.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  namespace: prod
  name: ns.prod-name.px-snap-restore
  annotations:
    volume.beta.kubernetes.io/storage-class: px-sc
    px/snapshot-source-pvc: ns.prod-name.px-snap-1
spec:
   accessModes:
     - ReadWriteOnce
   resources:
     requests:
       storage: 2Gi

The above example restores a volume from the source snapshot PVC with name ns.prod-name.px-snap-1.

Using inline spec

If you do not wish to use annotations you can take a snapshot by providing the source PVC name in the name field of the claim. However this method does not allow you to provide namespaces.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: name.snap001-source.pvc001
  annotations:
    volume.beta.kubernetes.io/storage-class: px-sc
spec:
  accessModes:
     - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Note the format of the “name” field. The format is name.<new_snap_name>-source.<old_volume_name>. Above example references the parent (source) persistent volume claim pvc001 and creates a snapshot by the name snap001.

Clone from a snapshot

You can restore a clone from a snapshot using the following spec file. In 1.3 and higher releases, this is required to create a read-write clone as snapshots are read only.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: name.rollback001-source.snap001
  annotations:
    volume.beta.kubernetes.io/storage-class: px-sc
spec:
  accessModes:
     - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Note we used used the existing snapshot name in the source part of the inline spec.

Using snapshots

Listing snapshots

To list your snapshots, use the pxctl volume list --snapshot command as follows:

pxctl volume list --snapshot

ID			NAME	SIZE	HA	SHARED	IO_PRIORITY	SCALE STATUS
1067822219288009613	snap001	1 GiB	2	no	LOW		1	up - detached

You can use the ID or NAME of the snapshots when using them to restore a volume.

Restoring a pod from a snapshot

To restore a pod to use the created snapshot, use the pvc name.snap001-source.pvc001 in the pod spec.

Managing snapshots through pxctl

To demonstrate the capabilities of the SAN like functionality offered by Portworx, try creating a snapshot of your mysql volume.

First create a database and a demo table in your mysql container.

mysql --user=root --password=password

create database pxdemo;

Query OK, 1 row affected (0.00 sec)

use pxdemo;

Database changed

create table grapevine (counter int unsigned);

Query OK, 0 rows affected (0.04 sec)

quit;

Bye

Create a snapshot of this database using pxctl

First use pxctl volume list to see what volume you want to snapshot

bin/pxctl volume list

ID					NAME										SIZE	HA	SHARED	ENCRYPTED	IO_PRIORITY	SCALE	STATUS
381983511213673988	pvc-xxxxxxxx-xxxx-xxxx-xxxx-7cd30ac1a138	20 GiB	2	no		no			LOW			0		up - attached on xx.xx.105.241

Then use pxctl to snapshot your volume

pxctl volume snapshot 381983511213673988 --name snap-01

Volume successfully snapped: 835956864616765999

You can use pxctl to see your snapshot

pxctl snap list

ID					NAME	SIZE	HA	SHARED	ENCRYPTED	IO_PRIORITY	SCALE	STATUS
835956864616765999	snap-01	20 GiB	2	no		no			LOW			0		up - detached

Now you can create a mysql Pod to mount the snapshot

kubectl create -f portworx-mysql-snap-pod.yaml

Download example

apiVersion: v1
kind: Pod
metadata:
  name: test-portworx-snapped-volume-pod
spec:
  containers:
  - image: mysql:5.6
    name: mysql-snap
    env:
      # Use secret in real usage
    - name: MYSQL_ROOT_PASSWORD
      value: password
    ports:
    - containerPort: 3306
      name: mysql
    volumeMounts:
    - name: snap-01
      mountPath: /var/lib/mysql
  volumes:
  - name: snap-01
    # This Portworx volume must already exist.
    portworxVolume:
      volumeID: "vol1"

Inspect that the database shows the cloned tables in the new mysql instance.

mysql --user=root --password=password

show databases;

+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| pxdemo             |
+--------------------+
4 rows in set (0.00 sec)

use pxdemo;

Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

show tables;

+------------------+
| Tables_in_pxdemo |
+------------------+
| grapevine        |
+------------------+
1 row in set (0.00 sec)