True disk-to-disk backups are usually controlled by backup software to create what is typically referred to as "near line" copies of the data. This also means that this copy must be written back to a specific location (restored) in order to be accessed. In addition, a solid backup scheme should typically include the creation of a (tape) copy of the backup data to be stored offsite. For these reasons, the availability and performance of the disk array for backups becomes secondary. One of the appealing aspects of disk-to-disk backups is that they offer better overall performance than tape backups but at a lower cost than data replication.
Therefore, pricing is probably one of the main evaluation criteria followed by scalability when considering the selection of disk storage to use for disk-to-disk backups. These last points are at the base of the growing popularity of ATA and SATA disk technologies for disk-to-disk backups.
This was first published in July 2004