What happens when the helium-filled disc is depressurized?

With the advent of helium-filled magnetic disks, a number of questions arise, the answer to which would allow us to give a balanced assessment of the latest achievements of science and technology. The main one, in our opinion, is the scenario of the drive behavior, whose thermocamera has replaced the atmosphere of inert gas with outboard air. The problem of helium leakage was the most difficult in the HDD development process and, despite the promises of manufacturers, it is still a burning issue in the context of operating costs.

To explain the processes occurring in the HDD containment zone, the hypothesis put forward in the article “ Helium cushion: the second breath of magnetic disks ” looks logical. The essence of the assumption is that the change in the density of the medium (recall that helium is six to seven times lighter than air) affects the distance between the head unit and the surface of the carrier. According to our data, this parameter is estimated at 10 nm. In the air due to a change in the lift, the “hovering” of the head above the plate is slightly higher than in the helium atmosphere. The spread is quite small, but with disastrous consequences. Their essence boils down to the fact that with the loss of helium, the chances of reading are high enough, while the probability of error-free recording is significantly reduced.

If the assumption made in the article is true, then there are at least two indisputable arguments confirming this. We present them briefly as follows:
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1. Reading is a procedure with checksum verification; if necessary, it will be repeated or repeated with a retrein.
2. Failure to write, unlike reading, can have fatal consequences for a large amount of data on the disk.

The subject of discussion may be arguments somehow related to magnetic recording technology. Unlike unsuccessful reading, the consequence of which can be easily corrected by repeating the operation (and when it comes to recovering data from a faulty drive, performance degradation due to the execution of repetitions is generally minor), the situation with a failed recording is much more complicated.

• It is more difficult to detect errors as well as eliminate their consequences. The fact is that when writing a more powerful magnetic field is required, therefore the distance between the head unit and the surface becomes a critical parameter. In addition, the recording head has a large size: it needs to transfer a more powerful effect for the carrier to magnetize.
• The readable data signal goes through the analog path to the amplifier. Such a system of electronic components, when properly designed, is sufficiently adaptive and capable of leveling out the effect of changes in the signal level and the appearance of interference within certain limits. When recording, the storage cells are domain structures on the disk surface. Even a small deviation from the specified magnetic parameters can lead to recording failure: the level of magnetizing effect will be insufficient.

We have everything.

The illustrations in the article are used to draw attention to the problems of helium-filled discs. They are borrowed from the following sources:

• Zhang G., Li H., Shen S, Wu S. // Simulation of helium-filled hard disk drive
• Sae Woong Killer, Joseph AC Humphrey, Hossein Haj-Hariri // Numerical study of the air-or helium-filled simulated hard disk drive