A disaster recovery (DR) volume is a special volume that is mainly intended to store data in a backup cluster in case the whole main cluster goes down. Disaster recovery volumes are used to increase the resiliency of Longhorn volumes.

For a longer explanation of how DR volumes work, see the concepts section.

For disaster recovery volume, Last Backup indicates the most recent backup of its original backup volume.

If the icon representing the disaster volume is gray, it means the volume is restoring the Last Backup and this volume cannot be activated. If the icon is blue, it means the volume has restored the Last Backup.

Warning: Disaster recovery volume on XFS filesystem cluster

The DR volume data can differ from the backup on the XFS file system. This is due to the finding in https://github.com/longhorn/longhorn/issues/2503#issuecomment-828158607.

If your cluster is already on the XFS file system and needs to restore from backup before the upgrade. We suggest restoring to an ext4 filesystem cluster to avoid data loss.

Creating DR Volumes

Prerequisites: Set up two Kubernetes clusters. These will be called cluster A and cluster B. Install Longhorn on both clusters, and set the same backup target on both clusters. For help setting the backup target, refer to this page.

1. In the cluster A, make sure the original volume X has a backup created or has recurring backups scheduled.
2. In backup page of cluster B, choose the backup volume X, then create disaster recovery volume Y. It’s highly recommended to use the backup volume name as the disaster volume name.
3. Longhorn will automatically attach the DR volume Y to a random node. Then Longhorn will start polling for the last backup of volume X, and incrementally restore it to the volume Y.