New Light On Tape Technologies.

Demystification of tape technologies

This article is the second in a two-part series. The first part appeared in the December 2000 issue of CTR.

Sony's AIT technology has gained strong market acceptance in recent years based on its high capacity, fast data access, and low price. The current generation, AIT-2, offers customers 50GB of native capacity on a compact 8mm cartridge using Advanced Metal Evaporated tape. The innovative Memory-in-Cassette feature stores tape file directory information on a memory chip that the drive can read directly and then go to that exact location on the tape. This capability dramatically decreases file search and access times. Sony recently announced mid-2001 availability for their next generation AIT drive, AIT-3. It will provide 100GB of native capacity and 12MB/sec data rate fulfilling Sony's roadmap projecting a doubling of capacity and throughput every two years.

Overland's AIT Library-Pro--the company's first AIT product--was also the industry's first modular scalable AIT library, offering more than 20TB of compressed capacity. Overland has announced intentions to offer an AIT-3 version of the LibraryPro when it is available in 2001.

Mammoth

As another high-capacity format seeking to take market share from the industry leader DLT, Exabyte's Mammoth 2 is currently the highest-capacity helical scan format available with a native capacity of 60GB and a native transfer rate of 12MB/sec. With similar pricing to DLT 8000 yet offering 50 percent higher capacity, Mammoth 2 has emerged as yet another competitor for midrange and enterprise tape automation applications.

4mm DAT 

DDS-4 is the latest incarnation of 4mm DAT technology based on the Digital Data Storage (DDS) standard. Aimed at workgroup departmental server applications rather than midrange and enterprise markets targeted by AIT and Mammoth, DDS-4 provides 20GB of native capacity on a single DAT cartridge while boosting data rate performance to 3MB/sec. Overland is a major player in the DDS market with the WangDAT 9400 Series available in the DDS-4 format. Overland also offers WangDAT models in DDS-3 and DDS-2 formats.

Automation Considerations

While some of the newest tape drives are specifically designed to ease implementation into automated environments, virtually all tape formats may be found in automated products. Even though this is true, a customer should keep in mind that the duty cycle capabilities of tape drives differ significantly. Using a tape drive in an automated environment with too low of a duty cycle capability in an application will result in drive failures due to the drive literally "burning out".

The technical specifications of a tape drive indicate how high a duty cycle it will best operate in. The specifications that will assist you in matching the best drive for your application include MTBF (Mean Time Between Failure, hours), recording head life (hours), MSBF (Mean Swaps Between Failure, in cycles), and media durability (number of passes). The MTBF for tape drives for entry to mid-range automation applications are usually rated at a 20% duty cycle and range between 200,000 and 300,000 hours. Drives that are in this category include Travan NS and DDS. Drives capable of high duty cycle applications are usually rated at 100% duty cycle and around 250,000 or more hours for MTBF. Drives capable of medium to high duty cycle applications include DLT, SDLT, AIT, Mammoth, LTO Ultrium, 9840, and Magstar.

Summary

The benefits of tape automation are plentiful--massive increases in available capacity, better data protection with automated backup procedures to eliminate operator errors and increased drive reliability through robotic media handling. Overland's leadership in tape automation is the result of the years of experience and innovation combined with matching the right tape technology for the right application.

Jim Jenkins is the director of product marketing at Overland Data, Inc. (San Diego, CA).