Virtual tape library
(also VTL, virtual tape system, VTS)
Virtual tape library definition
A virtual tape library (VTL) is a storage system that mimics a physical tape library — only it uses a hard disk or other storage media. It allows backup software to store data as if it’s writing to actual tapes, while in reality, it’s writing to a faster disk-based storage.
See also: backup, storage virtualization, host virtual machine, data center virtualization
History of virtual tape libraries
The concept of VTLs emerged in the late 1990s and early 2000s. As data volumes grew, the time taken to back up and restore data from physical tapes became a challenge. VTLs helped make use of the speed of disk storage and maintain compatibility with backup software that expected tape storage.
Over time, as backup technology evolved, VTLs started incorporating deduplication to optimize storage.
How a virtual tape library works
- The VTL system presents itself to the backup software as if it were a real tape library, complete with virtual tape drives and tape cartridges. This means the backup software believes it’s writing to or reading from physical tapes.
- When a backup operation starts, data is written to the VTL as if to a tape. However, the data is actually saved on high-speed disks, making the operation faster.
- During a restore operation, the VTL retrieves data from the disk storage, again much faster than it would from physical tape. The backup software isn’t aware of the difference.
- Some VTLs have deduplication features, which identify and remove redundant data. This means only unique data is stored, maximizing storage efficiency.
- If needed, data from the VTL can be exported to real physical tapes for offsite storage or long-term archival.
- Many VTLs can duplicate their data to another VTL at a separate location for added data security.
Benefits of virtual tape libraries
- Speed. Disk-based backups through VTLs are faster than traditional tape backups, reducing backup windows.
- Quick restores. Data restoration is faster from disks compared to tapes.
- Compatibility. VTLs work with existing tape-based backup software while offering disk-based storage speed.
- Deduplication. Many VTLs offer data deduplication, reducing storage needs by removing redundant data.
- Offsite replication. VTLs can replicate backup data to another location for disaster recovery purposes.
- Transitioning. For businesses phasing out physical tapes but not ready to change their entire backup process, VTLs serve as an intermediate step.