Release Notes

9 Dell PS Series Snapshots and Clones: Best Practices and Sizing Guidelines | BP1027
3 Protecting data with snapshots and clones
3.1 Snapshots
Snapshots are point-in-time copies of volumes that capture the contents of a volume at a specific point in time
and are often used to recover data lost by events such as human error, viruses, or database corruption. They
can also be used for testing or to create a source for backup to tape or another disk. The creation of a
snapshot is done without disrupting normal host access to the volume. Snapshots have some features and
properties similar to the base volume as well as some unique capabilities.
When a snapshot is created, it does not consume any space, but instead is only a set of pointers to the data
in the base volume. As data is modified on the base volume, disk space is allocated from the snapshot
reserve to store the changes. Meanwhile, the snapshot still points to the original data pages so that the
volume looks exactly like it did at the point in time when the snapshot was taken.
Like volumes, a snapshot can be assigned an iSCSI Qualified Name (IQN) and can be presented as a volume
to a host. This allows a host to mount a snapshot, read or modify the data in the snapshot, or create a full
volume (clone) that has dedicated space allocated to it from the free storage pool.
Figure 1 illustrates a view of a volume with multiple snapshots over a period of time.
Multiple snapshots over time