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Most virtual tape libraries will accelerate backups, but there are key differences among them when it comes to scaling, interoperability and management.

For a growing number of organizations, a virtual tape library (VTL) provides a cost-effective addition to their disk-based backup. By storing data to disk rather than tape, the VTL speeds data backup and retrieval without requiring users to change their existing backup processes. This is because, to the backup server and backup application, the VTL looks like a traditional tape library. Benefits include squeezing ever-larger data sets into tight backup windows, retrieving data quickly when required for legal or regulatory reasons, and reducing the operational and reliability risks related to tape.

However, not all VTLs are created equal. The larger and more complex the storage environment, the more attention users should pay to how the VTL provides scalability, performance, manageability and deduplication which, by storing only unique bits of data, can reduce disk capacity and bandwidth needs by as much as 30:1 or 40:1 (see "Enterprise VTL feature checklist," below).

For some users, VTLs may be outright replacements for existing tape libraries, eliminating the cost of manually handling tapes, delays associated with the need to sequentially read through an entire tape to find data, and the resulting

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breakdowns when tape jams or breaks.

Michael Grillo, principal IT engineer at Foxwoods Resort Casino in Ledyard, CT, is looking forward to using his 80TB of VTL capacity to completely replace tape because of the VTL's increased reliability and speed. He backs up 4.5TB to 5TB each day. "Our next step is to replace tape with a VTL at our disaster recovery [DR] site that's nine miles from the main data center," he says.

Some VTLs are sold as "appliances" with preloaded software that may also be preconfigured for a specific storage server, while others are sold as software that can be installed on generic servers. The advent of deduplication has made disk-based VTLs an affordable fit for very large-scale storage and for data replication to remote sites over WANs.


Enterprise VTL feature checklist

  • Modular upgrades. So you don't have to buy a separate virtual tape library (VTL) for each increase in storage capacity.


  • Deduplication method(s), inline or post-processing, to meet your needs.


  • The ability to set common rules or perform common management functions across multiple VTLs.


  • Support for your backup software and hardware.


  • Reliability features such as clustering and failover.

This was first published in August 2008

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