Part two: Should you abandon DDS for AIT?

In Part 1 of "Should you abandon DDS for AIT?" we looked at five factors that need to be considered when looking at DDS vs. AIT. Those were: total storage capacity, backup transfer rates, available space, budget and retrieval capabilities. In this installment we see how AIT systems stack up with respect to the key factors listed above.

Capacity: AIT format tapes are available today with native capacities from 25 to 100 GB. If the information can be compressed, the native capacities jump by a factor of 2.6 to achieve up to 260 GB per cassette. Late next year, plans for the next generation of AIT-4 will hold 200 GB native per cassette. A full range of AIT automation solutions are available, too, from 16 tapes to more than 10,000 tapes. AIT is the foundation for automated solutions from a variety of vendors, including ADIC, GRAU Data, QualStar, and Spectra Logic. Because of this range, AIT solutions can meet user capacity needs from small business all the way through full enterprise. But note that bigger is not always better. For some users, an important AIT feature is the ability of the second and third generation drives to use lower capacity, previous generation tapes.

Transfer Rate: Native AIT drive transfer rates currently range from 4 Mb/sec (AIT-1) up to 12 Mb/sec (AIT-3). Compressed rates can exceed 30 Mb/sec, and burst rates can reach 80 Mb/sec. These rates are sufficient for nearly all business data backup and information storage needs, including video-on-demand.

Space efficiency: The drives are a compact, half-height, 3.5" form factor -- the smallest in the storage industry. Compact rack-mount AIT libraries are available that are only 1U and 2U high. Over time, most of your space requirement will be made up of your recorded tapes. AIT tape cassettes are a small, 8mm size that can easily fit in your shirt pocket. AIT-3 tapes have about the same capacity as LTO or SuperDLT tapes, but are only 40% of their size. And, as the future generations are released, the drives and tapes will remain exactly the same size.

Cost: AIT systems are very economical. For workstation-level use, AIT-1 drives are priced comparably to DDS systems (under $1000), but offer far higher performance. For more demanding applications, or for LAN-level storage, AIT-2 drives offer more performance, but remain below $2000. And even the latest generation AIT-3 drives are solidly in the midrange at about $4000. Media prices are affordable, too, running about $1.00 per native GB. When you take into account the other relevant factors, such as higher compression levels, reduced cleaning and maintenance requirements, and longer read/write head and media lifetimes, the overall cost of an AIT system is extremely attractive, and far less than competitor systems. What's more, the cost and effort of transitioning to a new format is further eased by software designed for that purpose. For example, NovaStor Corp. designed its TapeCopy software to migrate data from one tape format to another.

Retrieval performance: Compared to other storage formats, AIT loads faster (10 seconds), seeks faster (27 seconds), and unloads faster (10 seconds). Other high capacity storage formats, like LTO and S-DLT have seek times twice as long, or longer. For any particular retrieval task, the difference in times may seem small, but the more interactive the application is, the more this time difference will pay off. Even in pure backup applications, where stored information is not intended to be retrieved except in case of loss, the ability of a function to be up and running quickly depends on the ability of the backup system to access and retrieve the most important information first.

The AIT format may be a suitable choice for many current DDS users, especially since they are already familiar with the performance and reliability of helical-scan systems. Homework is imperative, but if you understand what each tape storage format can offer, and how that performance can map into your company's business objectives, success will be certain.

Based in San Jose, Calif., Michael Nixon is a senior manager in the Storage Solutions Business Group of Sony Electronics' IT Products Division.

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