Disk-to-disk-to-tape (D2D2T) is a type of computer storage backup in which data is copied first to backup storage on a disk and then copied again to a tape media. This two tiered approach provides a quick short term recovery option since backup data can be easily retrieved from disk, as well as a more reliable long-term archive and disaster recovery on tape, since tape media can be stored off-site.
But using tapes has its drawbacks. Tape handling is one of them. Since it is usually a manual process, the possibility of human error is apparent – tapes getting misplaced, tapes getting lost or damaged while being transported to an off-site location, personnel forgetting to make backup to tape, failing backups because of tape device error or not enough space on tape, etc.
One alternative to D2D2T which is gaining popularity these days is disk-to-disk-to-cloud (D2D2C). With a D2D2C approach, the tape tier of D2D2T is simply replaced with cloud storage. A D2D2C backup involves backing up server drives to disk-based storage, and then running scheduled backups to archive backup data off to a cloud-based location. For short-term recovery operations, backups from disk are used for restoration.
The advantages of using D2D2C are: no more manual handling of tape media to send off-site, thus eliminating human tape handling error; provides easier and faster options for restoring data (tape restore can be a step-by-step manual process: retrieve tape from off-site location, mount tape, search backup catalogue, restore data); data can be restored anywhere; data transfer to the cloud can occur during off hours which will not impact the business; and cloud backups are usually incremental in nature which will reduce the amount of data sent over the network.
However, there are also some disadvantages of using D2D2C. For small offices especially, sometimes the WAN or Internet bandwidth can be a limiting factor. Also, backup to the cloud is still relatively expensive.