Virtual Tape Libraries: The Best of Tape and Disk Backup

Tape backup has traditionally been the mainstay of enterprise data protection when long-term data protection is required. As disk technologies have improved and economies of scale have driven down prices, disk adoption rates have surged and it would appear disk is poised to eclipse tape as the dominant backup platform and relegate tape to a minor archival and disaster recovery role. Numerous surveys of the enterprise have indicated adoption of disk-based backup reached the ninetieth percentile by the end of 2005 and that disks will soon be the dominant backup medium for the enterprise. But the flexibility, plunging costs, and commoditisation of disk has quickly led to a proliferation of ad hoc and confusing disk backup implementations which fail to provide many of the core data protection benefits of tape and even introduce new problems in an organisation’s backup regime. This article quickly reviews the disk-versus-tape debate, examines simple disk backup’s pros and cons, and proposes the virtual tape library (VTL) using disk as the backup medium as the best replacement for traditional tape backup. Finally, it discusses why all VTLs are not created equal and what to look for in a VTL when considering one for enterprise tape backup replacement.