I have not used Sanpshot technologies with backup softwares, but can tell you the background information.
A LUN from SAN array can be assigned at any given time only with one Server or with Servers within Cluster. So, while backing up the data from that LUN, data flow will be from Storage --> Server Assigned with the LUN --> Backup Server / Media Server --> Tape.
1) With the use of Snap Shots, snapshot of any LUN can be taken and assigned to another Server (which generally will be master/media servers) so that the backups can be taken from there without effecting the production LUN. Snapshot can be removed once the backup is completed.
2) Incase if the tape backup is not required, Snapshot session can be continued for more time and the Snapshot can be considered as a backup copy/Point In Time copy residing inside the storage array itself. But Snapshot or Reserverd LUNs assigned for Snapshot operation can grow larger/filled up quickly incase so many changes are happening to Source LUN. And also the write requests to source LUN will be processed a bit late, as the existing data must be copied to reserved LUNs and pointer needs to be updated in SnapshotDB before making any changes.
So, the way you can interpret Storage Snapshot technology depends on your storage infrastructure and tape backup requirements.
I hope the information provided is clear enough to understand...
