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D2D, or disk-to-disk, is an effective and superior backup strategy that utilizes hard disks as the storage medium, rather than traditional tape media systems.
With the price of hard disks falling while capacity and speed continue to rise, using additional hard disks for D2D backup has become the proverbial no-brainer for individuals and companies interested in protecting their computer systems. The advent of RAID (Redundant Array of Independent Disks) has also contributed to D2D backup strategies. Motherboards that support advanced varieties of RAID utilize multiple disks in a variety of ways to increase speed, provide redundancy and offer error correction. In both RAID and non-RAID environments, D2D backup has several advantages over tape or optical storage.
There are two types of D2D: true D2D and virtual tape library or VTL D2D. The latter is not true D2D because it maintains a tape-like index of files. Though faster than tape, it still incorporates many of tape's limitations.
Tape storage, while serving a vital purpose, had many inconveniences and shortcomings. If a file needed to be restored, for example, the first task was to locate the appropriate archived tape cartridge. The tape then had to be read by the tape unit, a process that could take several minutes. When the file was finally located, it could be transferred, but even this process was often slow. Other problems included bad cartridges, tape wear and tear, and tape units malfunctioning.
Compounding these concerns, operating systems, programs, multimedia files and networks keep growing, making the idea of restoring a system even more foreboding. The slow process of backing/restoring with tape has become increasingly insufficient.
Thanks to affordable, high capacity hard disks, D2D is the perfect solution for backup. Whether using a RAID array for a large corporate network, or an extra hard disk as a shadow drive, D2D can outshine other backup strategies ten to one.
D2D provides "instant" backup and restore because the system recognizes the backup files as originals. There is no tape to tear, wear or scan, and no extra unit to malfunction. The files are always handy, restorable with a simple double-click, with no need to maintain external archives, as in the case of tape cartridges. D2D used with SATA (Serial ATA) RAID also provides for hot-swapping, when internal pre-emptive monitoring routines warn that a disk is 'going bad.' Furthermore, D2D has full scalability, with the capacity of a disk array reaching into the terabytes. In short, there is no viable drawback to using D2D, and several advantages.
There are software programs to automate D2D backup. Arctor, by byteplant GmbH, is one of the more popular and can accommodate RAID or non-RAID D2D strategies. This software can be downloaded for a free trial and is about US$40 to buy. If looking for network solutions, more robust software is also available. A search of your favorite software libraries or the Web will reveal many choices.