snapshots

Snapshots are point-in-time copies of a volume. Snapshots are managed the same way you manage volumes. In reality, snapshots are volumes: they can be accessed by initiators, are subject to the same controls, can be modified, and have the same restrictions as volumes. Snapshots can be cloned and replicated. The initial snapshot uses no space: it shares the original data with the source volume. Each successive snapshot captures the changes that have occurred on the volume. The changed blocks are compressed.