Cutting through the tape maze


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Tape has always been the media of choice for file backup and archiving tasks. Its low cost, portability and simplicity of use make it a perennial favorite with storage administrators. Ongoing improvements in tape drive and media performance, capacity and overall reliability have helped tape maintain its dominating position as the medium of choice for most backup operations. Today, whether employed as an offline safe backup, or online archival storage in automated libraries, tape is an intricate part of any overall hierarchical storage management plan.

Following is a brief overview of the most popular tape choices for midrange systems and networking segments, and their technologies, performance parameters and costs. We'll then put on rose-colored glasses and peer into tape's future.

Major 8mm formats
8mm tape technology employs helical scan recording methodology and is a reliable method for storing large volumes of computer data. With this approach, data is written in short diagonal tracks across the width of the tape. This is the same type of recording technique used by videotape recorders. The full-tape (beginning-to-end) is written in one pass. Basically, helical scan devices utilize a tape transport system consisting of a two-reel cartridge and a tape path that pulls tape over (and halfway around) a spinning read/write cylinder. Helical scan systems can achieve extremely high data densities and have proven field-reliable

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since they began wide-scale deployment in 1996.

8mm highlights
AIT-3 260GB 31.2MB 3.5" $4,000
Mammoth-2 150GB 30MB 5.25" $3,100
There are two major 8mm protocols relying on different drive technologies and compression algorithms - AIT and Mammoth. They are not compatible, so choosing an 8mm tape solution also means choosing a vendor.

Advanced Intelligent Tape (AIT). Developed by Sony, it's designed to support the upper-end midrange server market with a combination of data integrity, speed and capacity. AIT tape drive systems are primarily designed for use in tape libraries and robotic devices used in backup applications. AIT is known for its performance, media and Memory-In-Cassette (MIC) features.

Sony's new AIT-3 8mm tape product features fast (27 seconds) access, high-density tape recording (260GB, compressed) and reliable (50,000-hour head life; 30,000 tape passes) backup for large-scale network servers with large volumes of images and data to be protected. Sony AIT-3 drives provide a 31MB/s (compressed) data transfer rate at a media cost of approximately $0.38/GB.

AIT's Advanced Metal Evaporated (AME) media is a data-grade tape, with anti-corrosive properties that improve tape durability and reduce tape wear, extending media life to a 30-year archival rating. An AIT-3 media cartridge costs about $99/cartridge. Sony AIT drives are available in a compact 3.5-inch footprint (with standard frame mount optional). Interfaces supported include all versions of SCSI.

The MIC hardware consists of a 64Kb (AIT-3 models) erasable electrical programmable read-only-memory chip mounted inside the data cartridge. The MIC stores the tape system log, user-defined information and all of the file storage location data normally found on the first segments of tapes used in competing technologies. Because the MIC firmware gauges how far to fast forward or rewind, the drive electronics no longer must read individual address ID markers while the tape is moving. As the target zone approaches, the drive motor slows down to pick up the physical ID markers for fine positioning. The result is search speeds up to 150 times the normal read/write speed of the drive, resulting in lower average data access times. The MIC feature also provides an additional level of reliability, due to the duplication of file index search information.

Mammoth tape. This is Exabyte's 8mm entry into the high-end midrange server market, featuring a tape deck with 40% fewer parts than previous 8mm drives, a capstan-less design that improves reliability by reducing tape wear and support for AME media. Mammoth drives also feature self-calibration and automatic device monitoring for preventive maintenance and error recovery, accompanied by associated automatic reports.

A major benefit of Mammoth tape systems is its backward compatibility with previous Exabyte standard 8mm drives, libraries and media. Users can upgrade while protecting their investment in current equipment.

This was first published in July 2002

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