Disk-to-Disk (D2D) and Virtual Tape Libraries (VTL)

D2D is Short for disk-to-disk -a type of data storage backup in which the data is copied from a disk—typically a hard disk—to another disk—such as another hard disk or other disk storage medium. In a D2D system, the disk that the data is being copied from typically is referred to as the primary disk and the disk that the data is copied to typically is called the secondary or backup disk.

Contrast with D2T. One advantage of a D2D system over a D2T system is that backup files can be accessed directly just like any disk system. Tapes, conversely, have to be searched linearly and are not as expedient at retrieving data.

A VTL, or virtual tape library, is an archival backup solution that combines traditional tape backup methodology with low-cost disk technology to create an optimized backup and recovery solution. It is an intelligent disk-based library that emulates traditional tape devices and tape formats. Acting like a tape library with the performance of modern disk drives, data is deposited onto disk drives just as it would onto a tape library, only faster. Virtual tape backup solutions can be used as a secondary backup stage on the way to tape, or as their own standalone tape library solution. A VTL generally consists of a Virtual Tape appliance or server, and software which emulates traditional tape devices and formats.