UNIX System Administration Handbook - Evi Nemeth [111]
Travan tapes
Worth a brief mention here is the next generation of QIC tape technology, known as Travan. Travan drives use a linear recording technology and support media from 2.5GB to 10GB. The drives are inexpensive, but the tapes cost slightly more than those of other high-capacity tape systems, about $3/GB. The marketing hype claims a sustained transfer rate of approximately 1 MB/s.
Many manufacturers make Travan drives, but UNIX support is patchy. As of this writing, UNIX drivers are available for drives from HP, Tandberg, and Tecmar.
OnStream ADR
A relative newcomer to the tape drive scene is OnStream’s Advanced Digital Recording system. ADR is based on a linear recording technology and currently supports media sizes of 15GB and 25GB. The drives are cheap, and the cost of media is in line with other tape systems of similar capacities. The drives are pretty quick, too, with the 25GB model serving up 2 MB/s of throughput.
The original OnStream went out of business on March 16, 2001, but its assets have been acquired by a Dutch group that plans to continue selling the drives under the OnStream brand name. Nevertheless, the long-term prospects for this product are extremely uncertain. UNIX drivers for the devices are still somewhat new and are rumored to have some problems.
Currently, no autoloaders, jukeboxes, or stackers of any sort are available for the OnStream system.
DLT
Digital Linear Tapes are a popular backup device. These drives are reliable, affordable, and hold large amounts of data. They evolved from DEC’s TK-50 and TK-70 cartridge tape drives, which were popular peripherals on the DEC VAXstation. The first generation of DLT drives could read the old TK-70 tapes. DEC sold the technology to Quantum, which popularized the drives by increasing their speed and capacity and by dropping their price.
DLT tapes hold a lot of data, up to 40GB. Transfer rates run about 6 MB/s. Manufacturers boast that the tapes will last 20 to 30 years; that is, if the hardware to read them still exists. How many 9-track tape drives are still functioning and on-line these days?
The downside of DLT is the price of media, which runs about $65 per tape, although the prices are decreasing. For a university, this is a huge expense; for a Wall Street investment firm, it might be OK.
AIT
Advanced Intelligent Tape is Sony’s own 8mm product on steroids. In 1996, Sony dissolved its relationship with Exabyte and introduced the AIT-1, an 8mm helical scan device with twice the capacity of 8mm drives from Exabyte. Since the original product release, Sony has introduced two new products: a higher-capacity AIT-1 with an extended tape length, and a new AIT-2 drive. Sony plans to release AIT-3 in the near future.
The Advanced Metal Evaporated (AME) tapes used in AIT drives have a long life cycle. They also contain a built-in EEPROM that gives the media itself some smarts. Software support is needed to make any actual use of the EEPROM, however. AIT-2 claims a 6 MB/s native transfer rate with a media capacity of 50GB. Drive and tape prices are both on a par with DLT.
Mammoth
Exabyte’s Mammoth is an improved version of the 8mm tape system. Exabyte chose to develop and manufacture its own mechanism after its falling out with Sony. The Mammoth products still rely on Sony for the AME media, but the tapes do not contain a memory chip.
The first generations of the Mammoth line had reliability problems. However, Exabyte listened to their customers and improved the products. They now claim a failure rate of only 1%.
The original tiff between Exabyte and Sony was based on Sony’s poor manufacturing quality. Sony ran only one production line for both consumer products and data drives, so your Exabyte was essentially identical to your camcorder in Sony’s eyes. However, Sony seems to be ahead of the curve right now.
Mammoth-2 drives offer a blindingly fast 12 MB/s native transfer rate, far faster than other tape drives in this price range.
Jukeboxes, stackers, and tape libraries
With the low cost