Latest generation of magnetic tape offers massive storage.
Thirty or so years ago, virtually every home in the developed world had a collection of cassette and video tapes. With the advent of optical disks such as CDs and DVDs, followed by the spread of Internet downloads and streaming, magnetic tapes disappeared from our daily life. But tapes are still on active duty at data centers that store enormous volumes of data. Researchers are also making progress on storing ever larger quantities of data on them.
Artificial intelligence, cloud computing and big data are driving the latest in information technology. In contrast, magnetic tape has a retro image. At first glance, there would not appear to be much relationship between the former and the latter, but in reality there are very deep ties. For technologies such as AI that use vast quantities of data, reliable and easy-to-use data recording media are critical, and magnetic tapes are less costly than the hard disks and semiconductor memories that are the current mainstream in recording media.
The basic unit of recorded information capacity is the byte. Looking at the relationship between information capacity and media, one sees that magnetic tapes cost around $0.015 per gigabyte — one-quarter the cost with hard drives. Power consumption is one-thirtieth to one-tenth. Moreover, magnetic tapes can last for 30 years, nearly 10 times as long as a hard drive.
Consequently, there is solid demand for magnetic tape used in data recording. The volume shipped worldwide grew at a 20% year-on-year pace from 2008 through 2013, and jumped 30% in 2014. Cassettes with a common standard are used, and tape is wound around cassettes that are 10cm square and 2cm thick. The tape itself is around 850m long — 10 times as long as a 60-minute cassette tape. Under the current standard, such magnetic tapes can store 2.5 terabytes of uncompressed data, while the new standard expected to be rolled out within a year has a capacity of 6TB.
The structure of magnetic tape used in the latest data storage devices is not considerably different from that of conventional cassette tapes. The tape has four layers, with a foundation of plastic film, topped by a nonmagnetic layer made of a substance such as carbon black. This is coated with a magnetic layer containing a large quantity of fine magnets intermixed with adhesive — these minute magnets record the data. Lastly, a layer known as a back coat is formed on the reverse side of the tape so it can move smoothly.
How much data can be recorded on a given area of tape is determined by how many magnets are included in the magnetic layer. Recently, the two companies that lead the industry each announced new state-of-the-art technologies.
Fujifilm Holdings, which has an over 50% global market share, in April announced that, working with U.S. computer company IBM, it had developed technology that can store 220TB, 90 times the current standard. The technology uses barium ferrite (BaFe) with a particle diameter of around 20 nanometers. Because it is resistant to rust and therefore does not need to be coated with a rustproof material, it can be made very fine.
Performance is uneven if the sizes of the particles vary greatly, so the material was engineered with particle sizes ordered and arranged. The company made use of strengths it has accumulated in materials technology with photographic film. “One characteristic is that compatibility is high, as conventional products can be used as tape readers,” explained Fujifilm manager Kiyomi Ejiri.
In advance of this, world No. 2 Sony in spring 2014 developed technology for creating 185TB tapes using an entirely different format. Its primary characteristic is that the way magnets are attached to the tape is not the conventional mainstream approach of applying a coating of magnets mixed with adhesive, but instead uses the sputtering method.
In sputtering, a magnet is bombarded with ions, which knock off tiny pieces and sending them flying and sticking to the tape. The process is similar to vapor deposition. With this approach, it is possible to arrange the magnetic particles more neatly than with the coating method. However, it might be necessary to get new tape readers as well.
Both technologies have yet to be commercialized. Unlike hard drives, whose capacity is near maturation, “there is ample room for the [tape] technology to grow,” said Sony chief engineer Minoru Yamaga.
The companies that set data tape standards and manufacture readers are major U.S. IT companies such as IBM and Oracle, but the tapes themselves are made by three Japanese companies — Fujifilm, Sony and Hitachi Maxell.
Magnetic tapes are durable and economical, but they must feed through a tape reader, which takes more time than a hard drive. However, sometimes that’s OK — some data has a low usage frequency and does not necessarily have to be played back instantly. And the medium is safer — Google, which in 2011 accidentally erased a huge volume of email messages, was able to recover the data because it had been stored on tapes.