Home > Storage > PowerFlex > White Papers > Microsoft SQL Server Data Protection using Dell PowerFlex Snapshots > Overview of PowerFlex snapshots
Snapshots are a block image in the form of a storage volume or LUN used to instantaneously capture the state of a volume (or a group of volumes) at a specific point in time. PowerFlex snapshots are thin-provisioned and writable. That means that snapshots only consume capacity when changes are made to the original volume. Subsequent changes to the same data do not consume additional capacity. Once a snapshot is taken, it becomes a new unmapped volume in the system. It can be manipulated like any other volume that is exposed by the storage system: mapped, unmapped, renamed, resized, and so on. Writable snapshots mean that the snapshot volumes can be mounted to a server and used like other PowerFlex volumes for data read and write operations.
PowerFlex snapshots can be initiated manually through any of the clients including PowerFlex Manager UI, CLI, or REST API. The snapshots include the ability to create snapshot policies, which automate the creation and deletion of snapshots according to a predefined schedule of your own choosing.
Snapshots and their source volume are organized into a Volume Tree (V-Tree). The V-Tree includes the root volume and all descendant snapshots resulting from that volume. A V-Tree includes not only snapshots that are taken of the root volume at different points in time, but also descendants that are snapshots of snapshots. The following figure shows a small V-tree snapshot with all its descendant snapshots where S111 and S112 are snapshot of the root volume V1 at different times and S121 is the snapshot of S111 at some other time.
Figure 4. Volume tree of root volume V1 with all its descendant snapshots