Volume Snapshots

Volume Snapshots are copies of a persistent volume at a specific point in time. They can restore a volume to a previous state or create a new volume. Replicated PV Mayastor provides support for industry-standard copy-on-write (COW) snapshots, which is a popular methodology for taking snapshots by keeping track of changed blocks. Replicated PV Mayastor incremental snapshot capability enhances data migration and portability in Kubernetes clusters across different cloud providers or data centers. Using standard kubectl commands, you can seamlessly perform operations on snapshots and clones in a fully Kubernetes-native manner.

Use cases for volume snapshots include:

Efficient replication for backups
Utilization of clones for troubleshooting
Development against a read-only copy of data

Volume snapshots allow the creation of read-only incremental copies of volumes, enabling you to maintain a history of your data. These volume snapshots possess the following characteristics:

Consistency: The data stored within a snapshot remains consistent across all replicas of the volume, whether local or remote.
Immutability: Once a snapshot is successfully created, the data contained within it cannot be modified.

Currently, Replicated PV Mayastor supports the following operations related to volume snapshots:

Creating a snapshot for a PVC
Listing available snapshots for a PVC
Deleting a snapshot for a PVC

info

Unlike volume replicas, snapshots cannot be rebuilt on an event of a node failure.

Prerequisites#

Install and configure Replicated PV Mayastor by following the steps given in the Installing OpenEBS documentation and create disk pools.

Command

cat <<EOF | kubectl create -f -
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: mayastor-3
parameters:
  protocol: nvmf
  repl: "3"
provisioner: io.openebs.csi-mayastor
EOF

YAML

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: mayastor-3
parameters:
  protocol: nvmf
  repl: "3"
provisioner: io.openebs.csi-mayastor

Create a PVC by following the steps given in the Deploy a test Application documentation and check if the status of the PVC is Bound.

Command

kubectl get pvc

Example Output

NAME                STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS     AGE
ms-volume-claim     Bound    pvc-fe1a5a16-ef70-4775-9eac-2f9c67b3cd5b   1Gi        RWO            mayastor-3       15s

note

Copy the PVC name, for example, ms-volume-claim.

Create an application by following the instructions provided in the Deploy an Application documentation.

Create a Snapshot#

You can create a snapshot (with or without an application) using the PVC.

Follow the steps below to create a volume snapshot:

Step 1: Create a Kubernetes VolumeSnapshotClass object#

Command

cat <<EOF | kubectl create -f -
kind: VolumeSnapshotClass
apiVersion: snapshot.storage.k8s.io/v1
metadata:
  name: csi-mayastor-snapshotclass
  annotations:
    snapshot.storage.kubernetes.io/is-default-class: "true"
driver: io.openebs.csi-mayastor
deletionPolicy: Delete
EOF

YAML

kind: VolumeSnapshotClass
apiVersion: snapshot.storage.k8s.io/v1
metadata:
  name: csi-mayastor-snapshotclass
  annotations:
    snapshot.storage.kubernetes.io/is-default-class: "true"
driver: io.openebs.csi-mayastor
deletionPolicy: Delete

Parameters	Type	Description
Name	String	Custom name of the snapshot class
Driver	String	CSI provisioner of the storage provider being requested to create a snapshot (io.openebs.csi-mayastor)

Apply VolumeSnapshotClass Details

Command

kubectl apply -f class.yaml

Example Output

volumesnapshotclass.snapshot.storage.k8s.io/csi-mayastor-snapshotclass created

Step 2: Create the Snapshot#

Command

cat <<EOF | kubectl create -f -
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: mayastor-pvc-snap
spec:
  volumeSnapshotClassName: csi-mayastor-snapshotclass
  source:
    persistentVolumeClaimName: ms-volume-claim   
EOF

YAML

apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: mayastor-pvc-snap
spec:
  volumeSnapshotClassName: csi-mayastor-snapshotclass
  source:
    persistentVolumeClaimName: ms-volume-claim   

Parameters	Type	Description
Name	String	Name of the snapshot
VolumeSnapshotClassName	String	Name of the created snapshot class
PersistentVolumeClaimName	String	Name of the PVC. Example- `ms-volume-claim`

Apply the Snapshot

Command

kubectl apply -f snapshot.yaml

Example Output

volumesnapshot.snapshot.storage.k8s.io/mayastor-pvc-snap created

note

When a snapshot is created on a thick-provisioned volume, the storage system automatically converts it into a thin-provisioned volume.

List Snapshots#

To retrieve the details of the created snapshots, use the following command:

Command

kubectl get volumesnapshot

Example Output

NAME                  READYTOUSE   SOURCEPVC         SOURCESNAPSHOTCONTENT   RESTORESIZE   SNAPSHOTCLASS                SNAPSHOTCONTENT                                    CREATIONTIME   AGE
mayastor-pvc-snap   true         ms-volume-claim                           1Gi           csi-mayastor-snapshotclass   snapcontent-174d9cd9-dfb2-4e53-9b56-0f3f783518df   57s            57s

Command

kubectl get volumesnapshotcontent

Example Output

NAME                                               READYTOUSE   RESTORESIZE   DELETIONPOLICY   DRIVER                    VOLUMESNAPSHOTCLASS          VOLUMESNAPSHOT        VOLUMESNAPSHOTNAMESPACE   AGE
snapcontent-174d9cd9-dfb2-4e53-9b56-0f3f783518df   true         1073741824    Delete           io.openebs.csi-mayastor   csi-mayastor-snapshotclass   mayastor-pvc-snap   default                   87s

Delete a Snapshot#

To delete a snapshot, use the following command:

Command

kubectl delete volumesnapshot mayastor-pvc-snap

Example Output

volumesnapshot.snapshot.storage.k8s.io "mayastor-pvc-snap" deleted

Filesystem Consistent Snapshot#

The filesystem consistent snapshot ensures that the snapshot filesystem remains consistent while taking a volume snapshot. Before taking the volume snapshot, the csi-node plugin runs the FIFREEZE and FITHAW ioctls on the underlying filesystem to flush and quiesce any active IOs. After the snapshot creation process, the IOs are resumed.

By default, mayastor volume snapshots are fs consistent. This means that if any part of creating a snapshot or an ioctl fails, the whole process will fail and be tried again by the mayastor CSI-controller without any user intervention.

You can disable the fs consistency feature using the VolumeSnapshotClass parameter quiesceFS. See the below example to disable the feature:

kind: VolumeSnapshotClass
apiVersion: snapshot.storage.k8s.io/v1
metadata:
  name: csi-mayastor-snapshotclass
  annotations:
    snapshot.storage.kubernetes.io/is-default-class: "true"
parameters:
  quiesceFs: none
driver: io.openebs.csi-mayastor
deletionPolicy: Delete

info

Prerequisites#

note

Create a Snapshot#

Step 1: Create a Kubernetes VolumeSnapshotClass object#

Step 2: Create the Snapshot#

note

List Snapshots#

Delete a Snapshot#

Filesystem Consistent Snapshot#

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