Volume Snapshots

Explore this Page

Overview

Volume Snapshots enable point-in-time, consistent copies of persistent volumes managed by Replicated PV Mayastor. These snapshots play a crucial role in data protection, recovery, and portability strategies in Kubernetes environments. Leveraging a copy-on-write (COW) approach, DataCore Puls8 supports industry-standard snapshot capabilities that track changes at the block level to ensure efficient storage utilization.

DataCore Puls8 supports incremental snapshots, facilitating optimized backup and migration across heterogeneous cloud and data center infrastructures. All snapshot operations are seamlessly performed using native Kubernetes tools such as kubectl, providing a familiar experience for Kubernetes users.

Typical use cases include:

  • Backup and disaster recovery
  • Troubleshooting using cloned volumes
  • Development and testing against read-only data copies

Snapshots are:

  • Consistent: Data remains consistent across all volume replicas.
  • Immutable: Once created, snapshot data cannot be altered.

Snapshots are not reconstructable in the event of node failure, unlike volume replicas.

This feature is currently supported exclusively for Local PV ZFS.

Requirements

Before using Volume Snapshots, ensure the following requirements are met:

  • DataCore Puls8 with Replicated PV Mayastor is installed and configured.
  • DiskPools are created and operational.
  • A PVC is deployed using a compatible StorageClass.

Creating a StorageClass

Copy
Create a Mayastor StorageClass with NVMf protocol and 3 replicas
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

Create and Verify a PVC

Copy
Check the status of the created PVC
kubectl get pvc
Copy
Sample Output
NAME                STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS     AGE
ms-volume-claim     Bound    pvc-fe1a5a16-ef70-4775-9eac-2f9c67b3cd5b   1Gi        RWO            mayastor-3       15s

Copy the PVC name (ms-volume-claim in this case) for later use.

Ensure an application is deployed using the created PVC, as described in the Deploy an Application documentation.

Creating a Volume Snapshot

Snapshots can be created either with an active application or directly from the PVC.

  1. Define the VolumeSnapshotClass.

    Copy
    Create a default VolumeSnapshotClass for Replicated PV Mayastor
    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

    Alternatively, apply using a YAML file:

    Copy
    Apply the VolumeSnapshotClass definition
    kubectl apply -f class.yaml
    Copy
    Sample Output
    volumesnapshotclass.snapshot.storage.k8s.io/csi-mayastor-snapshotclass created

  2. Create the Snapshot.

    Copy
    Create a VolumeSnapshot from an existing PVC
    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
    Copy
    Apply the VolumeSnapshot configuration
    kubectl apply -f snapshot.yaml
    Copy
    Sample Output
    volumesnapshot.snapshot.storage.k8s.io/mayastor-pvc-snap created

    Snapshots on thick-provisioned volumes are automatically converted to thin-provisioned volumes.

Listing Snapshots

Use the following commands to view snapshot and snapshot content details.

Copy
List all VolumeSnapshots
kubectl get volumesnapshot
Copy
Sample 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

 

Copy
List VolumeSnapshotContent resources
kubectl get volumesnapshotcontent
Copy
Sample 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

Deleting a Snapshot

Use the following commands to delete a snapshot.

Copy
Delete a specific VolumeSnapshot
kubectl delete volumesnapshot mayastor-pvc-snap
Copy
Sample Output
volumesnapshot.snapshot.storage.k8s.io "mayastor-pvc-snap" deleted

Filesystem Consistent Snapshots

DataCore Puls8 supports filesystem-consistent snapshots by default. This ensures data integrity by quiescing active I/O operations using the FIFREEZE and FITHAW ioctls during snapshot creation.

If the filesystem quiescing process fails, the entire snapshot operation is retried automatically by the Mayastor CSI controller.

Disabling Filesystem Consistency

To disable filesystem quiescing, modify the VolumeSnapshotClass as follows:

Copy
Disable filesystem consistency by setting quiesceFs to none
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

Snapshot Space Requirement

When creating snapshots for an existing volume, each replica pool must have sufficient free space relative to the volume size. The minimum required free space is governed by the following configuration parameter:

Copy
Parameter to Set Minimum Free Space Requirement for Snapshots
openebs.mayastor.agents.core.capacity.thin.snapshotCommitment

This parameter specifies the required free space as a percentage of the volume size.

Example:

If the value is set to 40, and a pool has 40 GiB of free space, then the maximum volume size allowed for snapshot creation on that pool is 100 GiB.

Adjusting this parameter ensures that snapshots do not exceed the pool’s storage capacity, helping to maintain system stability and avoid failures during snapshot operations.

Benefits of Volume Snapshots

  • Enables point-in-time backup for critical applications.
  • Facilitates fast and reliable disaster recovery.
  • Minimizes downtime by enabling quick volume restores.
  • Simplifies data migration across environments or clusters.

Learn More