A chain of snapshots includes read-write snapshots descending from a read
only snapshot. The read only snapshots presents a constant view of the
data at the time the read only snapshot is created, and the read-write
snapshot starts with the view but can be modified by the user without
changing the view of its parent snapshot (e.g., the read only snapshot).
Accordingly, the read-write snapshot can be written for various testing
purposes while the read only snapshot remains undisturbed to preserve the
original data.