They do have limits: Although snapshot software has tremendous flexibility, snapshots do not offer the true data protection that is delivered by a backup application. Some vendors have begun to discover, however, that snapshot technology can be combined with traditional backups as a way of delivering some extraordinary features.
They can also be used with differencing disks during failover operations in order to help keep services available and avoid downtime for users. Using snapshots, users can make changes to what is stored on the differencing disks, and when administrators are ready to restore that data, those changes can be merged with the snapshot and restored back to the primary storage.
When a differencing disk snapshot is created, the snapshot becomes read-only. At that point, all write operations are redirected to a differencing disk. Vendors have discovered that some disk-based backups can be turned into snapshots. That way, snapshots can be used for a variety of purposes without having to work through a restore operation.
The snapshot technology protects the backup's integrity because write operations occur only on a differencing disk. This principle has been adapted to provide real-time failover and failback capabilities, as well as backup testing capabilities.
Snapshots can also be used in conjunction with traditional backup, such as with Microsoft Hyper-V, to test replicas of virtual machines without causing a conflict with any running primary virtual machines. In this video, watch a demonstration of how IT administrators can create a snapshot of a replica made with Hyper-V's replication service for testing purposes.