Virtual disk grafting and differential based data pulling from external repository

Abstract

A technique utilizes grafting and differential based (diff-based) data seeding to hydrate a special virtual disk (vdisk) on a multi-node cluster with data changes (differences) between a reference vdisk stored on the cluster and a snapshot stored in an external repository to enable failover (including failback) recovery of an application workload in a disaster recovery environment. The application workload is stored as a workload vdisk on local storage of the cluster and snapshots of the workload vdisk are generated and organized as a vdisk chain on the cluster. One or more snapshots of the vdisk chain may be replicated to the external repository using a long-term snapshot service. Each replicated snapshot may be backed up from the cluster to the external repository at the granularity of a vdisk, referred to herein as an external datasource disk. The special vdisk is a thinly provisioned, datasource-backed vdisk that is grafted onto the vdisk chain, e.g., as a child vdisk of the reference vdisk. The differences between the reference vdisk and datasource disk are seeded from the datasource disk to hydrate the datasource-backed vdisk.