Many storage device manufacturers are promising us that HAMR technology will allow us to see the storage needs of the future covered, with mechanical hard drives with capacities of more than 20 TB per unit but with the intention of exceeding 100 TB in the near future. Much is said, but do you know what HAMR technology is and how it works ? In this article we will tell you.
The word HAMR comes from the acronym for Heat Assisted Magnetic Recording , or heat-assisted magnetic recording, and as its name suggests it is based on the ancient principle of magnetic recording that has been used since the 70s in storage devices such and as we know them, but nevertheless now it promises that the amount of data that can be stored in a magnetic device will be significantly increased; A current “standard” hard drive is capable of storing about 1.14 TB per square inch, while with HAMR this density is increased to 6 TB / in2, so potentially up to 80 TB of capacity could be reached with current technology .
Let’s see how it works.
How does HAMR technology work?
In the following illustration, each region represents a bit where the colored ones can be 1 and the white ones can be 0, since as you know this system works with a binary information system. Normally, some of these regions become cluttered (magnetic orientation) leaving useless space that cannot be used. To improve the information density, HAMR uses heat to assist in the ordering of these regions and reduce the anisotropy (this is the difficulty required to change the magnetic orientation).
The first hard drive to exist used longitudinal recording (LR), which placed the magnetization in the same plane as the disc. The field we write with is the marginal field, where the deep field gap is filtered (see illustration).
As we increase the density of the area and reduce the size of the regions or “grains” where it is written, it was necessary to increase the anisotropy of the media, and yet as the media becomes more stable the writing becomes more difficult and A larger field is required to reliably change the direction of the grains in the middle and record the data. For 60 years, the field has been increasing from the magnetic recording head, but finally its natural limit was reached, it was not enough for more.
To build a device with HAMR technology, they had to make the following modifications:
- Add a laser diode to the head.
- Develop an optical path to direct laser light to the NFT.
- Integrate the NFT into the recording head.
- Develop new media compatible with HAMR.
- Modify the firmware of the unit.
- Adjust the manufacturing process.
- A million little details engineers spent countless hours working on.
From PMR to SMR and finally, HAMR
By using Perpendicular Magnetic Recording (PMR), it was possible to add a smooth base layer on the media and put the media in the “gap” of the head, where the field is largest and where each bit sits perpendicular to the heads. media rather than across the entire surface. The next evolutionary step was to design Shingled Magnetic Recording (SMR), which achieves greater area and density by “squeezing” the data tracks instead of reducing the bit size. The tracks overlap each other, like tiles on a roof, allowing more data to be written to the same space.
Because the drive head’s reader element is smaller than the writer, all data can be read on the clipped track without problems and without compromising data integrity. In addition, SMR does not require a significant investment for its development, which allows to implement hard drives with this technology while maintaining a low manufacturing cost.
On its own, SMR already brought about a 25% improvement in hard drive capacity with its introduction in 2014, but that was not enough and they also found that PMR was approaching the limits of storage technology. High anisotropy iron-platinum (FePt) media can overcome thermal stability problems with traditional PRM media and high area densities, but with conventional recording media you quickly run out of field to write in.
That’s where HAMR technology comes in, as it allows you to get around this limitation by literally heating up the medium. At room temperature the grains of the medium are small and thermally stable, just what we need, but heating them can temporarily reduce the coercivity of the media.
So, in summary, with HARM what you do is that the data is stored at room temperature, but before writing the medium is heated to reduce its coercivity and then it is cooled again, all this in less than 1 nanosecond. According to the manufacturers, HARM technology allows you to expand the density from 1 to 5 TB for each square inch of surface.
