The Fundamentals Of AIT Technology.

This column begins a semi-regular series written by a member company from the AIT Forum.

Sony Electronics introduced Advanced Intelligent Tape (AIT) technology in 1996. The AIT1 drive offered 25GB native (uncompressed) capacity and 3MB/sec native data transfer rate. A longer tape was later introduced that raised the native capacity to 35GB. The AIT1 tape drive design embodied a number of hardware and media advances that combined to deliver reliable, cost-effective performance for many mid-range tape users. In 1998, Sony introduced AIT2, the second drive on the AIT product roadmap, featuring a native capacity of 50GB and 6MB/sec data rate.

The AIT Drive

AIT technology combines advances in read/write head design, tape handling, error correction, and media construction to improve reliability and lower costs. In addition, the drive's 3.5-inch form factor and small tape cartridge format enable very compact packaging, especially in tape libraries: seven terabytes per square foot is readily achieved.

AIT read/write heads differ from older designs in a number of respects, particularly in the proprietary material used to construct the head, the design of the head profile, and the manufacturing technology developed to produce it. The net benefit of these developments is readily apparent in the drive's 50,000-hour head life specification.

Advanced data compression technology has been incorporated into AIT. Adaptive Lossless Data Compression (ALDC) has been utilized to achieve typical compression ratios of 2.6:1, versus the 1.7:1 ratios characteristic of older designs. Improved data compression performance means recording more data on each tape at higher transfer rates, reducing cost per megabyte stored and shortening backup times. Several features, including automatic head cleaners to eliminate periodic head cleaning and individual fans in each drive to reduce operating temperatures, enhance reliability.

AME Media

Advances in tape media are another key element of AIT technology. With AIT, Sony introduced the first Advanced Metal Evaporative (AME) tape. AME is a complete departure from previous magnetic tape construction techniques. Unlike Metal Particle (MP) tape, which depends on applying a layer of finely ground magnetic material in a chemical binder to the tape substrate, AME deposits a film of pure cobalt onto the basefilm without the use of a binder. The cobalt material is heated by an electron beam in a vacuum chamber and results in a vapor deposited magnetic surface, free of any impurities. AME has twice the magnetic flux density of coated media. This translates to improved levels of recording density and recording system performance.

To protect the recording surface, a DLC (Diamond Like Carbon) coating is applied, again in a vacuum deposition process. The DLC protective layer approaches the hardness of diamond and dramatically improves both abrasion resistance and overall tape durability. The increased durability and additional surface oxidation protection results in a low initial error rate and extended recording life. DLC is also an extremely smooth surface, contributing to increased head life.

The MIC Concept

AIT also introduced the first application of a flash memory chip incorporated within the tape cartridge to record system and user-related data directly to enhance performance, data access, and data reliability.

The Memory In Cartridge (MIC) hardware consists of a 64Kbit EEPROM that is mounted within the data cartridge and includes a 5-pin interface to the drive or other external connection. Using a serial interface to the memory chip, the AIT drives are able to store and retrieve selected information directly from the chip and use this to provide direct benefits to customer applications.

The MIC information consists of data written at the time of cartridge manufacture, data written when the media is first loaded into an AIT drive, portions updated as part of a read, write, or load sequence, and, finally, portions that can be written directly by a user's application. MIC can cut total data access time by up to 50 percent compared to conventional methods. Benefits of MIC include:

* Faster access to data with an innovative high-speed "fast forward" search speed that reduces average file access time to less than 30 seconds.

* Better reliability through predictive diagnosis of media degradation.

* Faster and more reliable access to volume serial information.

* Better data-set management through the use of user-specified volume and partition notes.

* Greater data integrity though a fault-tolerant system log.

* Enhanced media security through the use of decryption codes stored in the MIC.

Four years after introduction with tens of thousands of drives in service worldwide, the benefits of AIT are becoming more widely understood. Customer acceptance continues to accelerate and recent introductions by key OEMs further validate the AIT design concepts. AIT3 will be released late this year, once again doubling capacity and performance to 100GB and 12MB/sec, respectively. AIT3 will also offer a Fibre Channel interface.

Bob Covey is the vice president of marketing at Qualstar Corporation (Canoga Park, CA).