During every backup session, Veeam Backup for Nutanix AHV creates a snapshot for each VM added to the snapshot job or a protection domain snapshot if it is added to a protection domain snapshot job. The snapshot itself is a collection of point-in-time snapshots that Veeam Backup for Nutanix AHV takes using native Nutanix AHV capabilities.
A sequence of Nutanix AHV snapshots created during a set of backup sessions makes up a snapshot chain. Veeam Backup for Nutanix AHV creates the snapshot chain in the following way:
- During the first backup session, Veeam Backup for Nutanix AHV creates a snapshot that contains all VM data and saves it in the Nutanix AHV cluster where the processed VM resides. This snapshot becomes a starting point in the snapshot chain.
- During subsequent backup sessions, Veeam Backup for Nutanix AHV creates snapshots that contain only those data blocks that have changed since the previous backup session.
Each Nutanix AHV snapshot in the snapshot chain contains metadata. Metadata stores information about the protected instance and the job that created the snapshot. Veeam Backup for Nutanix AHV uses metadata to identify snapshots created by the Veeam backup service, to detect outdated snapshots, and to load the configuration of source VMs during recovery operations, and so on.
In Veeam Backup for Nutanix AHV, snapshots act as independent restore points for backed-up instances. If you remove any snapshot, it will not break the snapshot chain — Nutanix AHV will include data of the deleted snapshot to a following snapshot. Therefore, you will still be able to roll back instance data to any existing restore point. Note that while removing a protection domain snapshot, Veeam Backup for Nutanix AHV deletes data of all VMs and volume groups included in the domain.
The number of snapshots kept in the snapshot chain is defined by retention policy settings. For more information, see Retention Policy for Snapshots.