Disk-to-disk (or D2D) refers to the disk-to-disk method of backup storage. With D2D, a computer hard disk is backed up to another hard disk rather than to a tape. Disk-to-disk systems are random-access storage, not linear or sequential like tape storage. Thus, D2D can send and receive multiple concurrent data streams. Relative to tape backup, D2D offers shorter backup windows, faster restores and quicker access. Random access D2D systems allow more incremental backups per full backup. As a result, time-consuming full backups can be scheduled less frequently. Unlike tape, individual files can be recovered from D2D without scanning the entire backup volume.
Most disk-to-disk backup appliances allow copies to be moved from disk to tape storage for long-term data retention. Disk-to-disk-to-tape (D2D2T) is a backup scheme that copies data initially to a disk-based backup device. The same data is then periodically copied from the disk device to a tape storage system. The disk backup provides faster recovery than tape, while tape offers a more economical medium for archiving and off-site storage.
Open source software defined storage (SDS) solutions provide a lower cost disk-to-disk backup approach. Commodity hardware and per node pricing (rather than per gigabyte) keep backup costs down. Designed as a distributed storage cluster SDS provides unlimited scalability. Backup space can be added by purchasing another server license and adding a node to the storage cluster. Software defined storage solutions automatically integrate the new server and distribute the additional backup space. Enterprises with heterogeneous server environments can use SUSE Enterprise Storage to back up Linux, Unix and Windows servers.