Although disk-to-disk backup methodologies have become incredibly popular over the past few years, the vast majority of enterprises -- large and small -- still use the same tape backups they implemented years ago. As time goes on, however, more and more old-school backup implementations will reach a breaking point where either capacity or performance can't get the job done.
When you realize that tape can't cut it any longer, you'll likely consider using a disk-based backup appliance, which you can get from many vendors, such as EMC Data Domain, Exagrid, and Quantum. But when choosing the right appliance, be careful: Most buyers focus on the most efficient deduplication engine, but that's only one difference to explore.
The deduplication engine gets IT's attention because the whole point of implementing dedupe is to shrink the amount of storage you need to hold your backups -- to save both on physical storage costs and to gain longer on-disk retention times. But capacity efficiency is a relatively small issue in practice. Most of the significant operational differences are based on when in the backup cycle that deduplication takes place and how crucially important scalability is achieved.