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Why the future of data storage is still behind magnetic tape

Hard drives are approaching the limits of their development, and the film becomes only better with time.

Photo by Victor Prado

Financial institutions oblige companies to store more and more data and an increasingly long period of time. The amount of data that has to be stored each year grows by 30-40% compared to the previous year. The capacity of hard drives is also growing, but with half the pace. Fortunately, all this information does not require instant access, so the film is an excellent solution to the problem.

In general, a lot of information in the world is stored on film: scientific data on particle physics, astronomical data, national archives, cultural heritage, most movies and bank data. There are professionals (material specialists, engineers, physicists) whose work is to improve the ways of storing data on film.

For decades, the film developed no less than hard drives or transistors. The first film for storing information in digital form – the IBM model 726 – could store 1.1 MB on the coil. Today, one coil can store 15 terabytes of data, and one robotic film storage – 278 petabytes.

Of course, the film does not allow you to read information as quickly as hard drives or semiconductor memory. But it has its advantages.

  • The film is energy efficient: if the data is already recorded, the film does not require power to store it;
  • The film is reliable: the probability of errors in writing or reading is four to five orders lower than that of hard disks;
  • The film is safe: unlike discs that are usually connected to the computer all the time, cartridges with coils can be stored without connecting to devices, which protects the data from reading or modifying by intruders or the influence of human factors.

In 2011, due to an error in the software on Google servers , accidentally deleted mailin 40 thousand boxes. The deletion occurred on all backups on hard disks, because the error operation with the chain passed through them, but the letters were recovered from the tape. After this incident, it became known for the first time that Google makes backup copies on a tape, and then Microsoft confirmed that IBM’s film equipment is used in their Azure cloud service .

Magnetic film was first used to record the computer data of Univac in 1951. Getty Images

To store data on a film is six times cheaper than on hard disks, so it is used everywhere, if it is a question of large volumes of information. Since the film has practically disappeared from the consumer market, most do not know how fast it develops and will develop in the foreseeable future.

The film survived, because it is cheap and cheapens with time. It can be assumed that once the data compression on hard drives goes down, then the same applies to the film, because it uses about the same technology (only the older one). It’s like Moore’s law, but for a magnetic film. But this is not the case: over the years the pace of compaction of the record on the film does not subside, but persists around 33% per year. That is, doubling the amount of data recorded on the film occurs approximately every two to three years.

Physically, the technology of recording to hard disks and films is the same: the data are recorded on the magnetized surface by narrow tracks, on which polarity switching occurs. The information is recorded by a bit sequence. Since the advent of film and hard drives in the 50’s, manufacturers of both tend to more density, speed and cheapness, so the cost of storage in dollars per gigabyte decreased by orders of magnitude. Precisely because production is trying to reduce the price, the recording density per square millimeter is growing.

The more funding for research and development is received by companies manufacturing magnetic media, obviously, the more these media are progressing. Now on the most advanced hard drives you can write 100 times more information than on the same area of ​​the film. But since the very area on the film in the coil is much larger, it accommodates up to 15 TB of data , which is more than any existing discs on the market. In this case, the dimensions of the cartridge with the coil of the film and the hard disk are approximately the same.

Outside and inside: A modern cartridge contains one coil. After installing the cartridge, the film is automatically fed to the reading or writing device. Photo by Victor Prado

In addition to the capacity of the film and hard drives, there is one more difference: the speed of access to the data. In the coils are magnetic tape length of several hundred meters, the average time to access data – from 50 to 60 seconds. Hard drives have this time – from 5 to 10 milliseconds. However, the recording speed for a film is twice as high.

In recent years, the rate of compaction on disk records has decreased from 40% to 15% per year. The reason is fundamental physics. To write more data to the old area, you need to reduce the area for writing each bit. As a consequence, this reduces the strength of the signal while reading the data. If the signal strength is too low, it can be mixed with magnetic noise from neighboring magnetic beads covering the disk surface. You can reduce the noise by making the pellets themselves smaller. But then the granule will be so small that it can hardly keep its magnetization state stably. The smallest size of granules, suitable for magnetic recording, has already been reached, in the professional field it is called the supermagnetic limit .

Until recently, the achievement of this limit remained unnoticed for consumers, because manufacturers added additional disks and heads for writing and reading inside the container, making the hard disk of the previous size, but larger. However, now more discs inside the container are difficult to add, preserving its dimensions, so the limit becomes more noticeable.

There are alternative methods of recording on the magnetic surface, which theoretically can overcome the supermagnetic limit. This is a record, accompanied by heating of the pellets , and a microwave recording . But it is difficult in the engineering and financial aspects. The company Western Digital has announced a hard disk with a microwave recording method, which it is going to release in 2019 . It is expected that such an innovation will keep the pace of compaction of the record in the region of 15% per year.

At the same time, the storage on the film is still far from reaching the supermagnetic limit, so the film can evolve for decades without going into its Moore’s Law and the limitations of fundamental physics.

The film has a cunning nature. Changing the cartridges with reels in the recording equipment, thin polymer material, parallel recording on 32 tracks – all this creates difficulties in the design of this data carrier.

In 2015, IBM, in cooperation with FujiFilm Corporation , discovered that recording with ultra-small barium-ferritic magnetic particles perpendicular to the film surface can achieve 12 times the density of other technologies. And in 2017, in cooperation with Sony, it was possible to achieve a density 20 times higher than the most modern hard drives. In the future, for film companies, for example, this will allow storing all the material of a high-budget film in just one coil instead of a dozen.

Flooding data: modern film stores contain hundreds of petabytes of data, and IBM's 726 model, introduced in 1952, could only save a couple of megabytes. IBM Photos
Flooding data: modern film stores contain hundreds of petabytes of data, and IBM’s 726 model, introduced in 1952, could only save a couple of megabytes. IBM Photos

To achieve this progress, engineers have adapted the heads for reading and writing to move along extremely narrow tracks on a film – about 100 nanometers wide. In addition, we had to make reading heads narrower – about 50 nanometers wide. When reading, the signal-to-noise level also decreased, so I had to manipulate the size and position of the magnetized pellets and the smoothness of the film surface, and also improve the signal processing and reading errors.

In order to ensure the reliability of recorded data for decades, engineers have developed new recording heads that produce much stronger magnetic fields than conventional ones.

Combining all these developments, IBM engineers managed to achieve a recording density of 818,000 bits per linear inch (this density measurement has historically been developed). The new technology allowed to fit on one inch of 246.2 thousand recording tracks and provided space for 201 gigabit per square inch. The cartridge with 1140 meters of film on the reel can store 330 terabytes of information. This can be compared to a whole cart of hard drives.

The storage industry consortium , which includes HP, IBM, Oracle, Quantum and several research groups, in 2015 released a document on plans for the development of data storage on film. According to the forecast of the consortium, by 2025 the recording density per square inch will grow to 91 gigabytes, and by 2028 – to 200 gigabytes.

Authors of the document are professionally interested in such an optimistic forecast, but it is quite realistic. The IBM laboratory confirms that 200 gigabytes per square inch is an achievable goal for the next decade.

The film is the carrier of information, which “Moore’s law” will press the last. Therefore, the benefit of storing data on a film compared to hard disks will increase in the years to come.

Note: The author of the article, Mark Lanz, works as a manager in the IBM laboratory in Zurich and deals with problems with storage of data on film.

The article was originally published in hard copy under the heading “Tape Storage Mounts a Comeback”, and then published on the IEEE consortium website .

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