Virtualizing tape library with VTL

VTL is high-speed disk storage presented as tape. It appears to the backup software and application as physical tape library. No changes are required in backup software and backup strategy and process. It eliminates tape sharing between servers, thereby improving restore performance. With no physical tape limitations, more backup jobs can be run in parallel. It avoids mechanical failure so common in tape drives. VTL works in conjunction with tape backup solutions and is not meant to replace it completely.

First generation of VTL suffered from the following drawbacks. Tapes can serve the purpose of remote archival vault, which VTL does not provide that option. Scalability of VTL is very costly as it requires adding controllers or expansion unit. Complexity added to implementation headaches. Inadequate support for data compression due to processing capacity and bus architecture limitations. No support for data de-duplication.

Problem with tape backup are lengthy backup and restore times and media and drive failures. These issues have pushed tape to perform long term archival and DR backup instead of normal production backup.

DataDirect Networks provides a Silicon Storage Appliance (S2A) which is a second generation VTL product. It is particularly suited to large sequential data I/O common in backup operations. For archival or DR purposes, where tape is still required, backup can be first done to this appliance before it can be moved to tapes during non-office hours. The product can also run a backup software (Hosted Backup option), thereby eliminating the need of a backup server and reducing cost. The appliance supports automatic tape caching, where it caches data going to physical tape, increasing performance. It supports data compression before storing it in disks. It is based on commodity SATA storage.