Friday is here, and the "A Taste of Science for the Weekend" corner is back — number 87.
This time: how the European Union, data centers, and physics are bringing HDD drives back to life.
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HDD drives are the large, older-style hard disk drives that were replaced by SSDs, now installed in virtually every electronic device we use.
HDDs store data by changing the orientation of magnetic grains on spinning metal platters, with a magnetic head reading and writing data on them. This architecture is particularly prone to failure and is notably slow.
Their main advantages have remained an attractive price point and relatively low wear, which is why they can still be found as a common storage medium in data centers.
The shift to SSDs made these drives largely obsolete, and their prices had been falling steadily — until recently, when a new EU AI regulation unexpectedly changed the picture.
The regulation requires that logs of user interactions with artificial intelligence be retained for 10 years, which in practice creates a regulatory mandate to store enormous quantities of data.
Add to this the surge in SSD prices driven by demand for AI servers, which has widened the price gap between SSDs and HDDs even further.
HDD drives suddenly began flying off the shelves, and nearly the entire next year's production has already been purchased.
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HDD drives are generally limited to 24 TB, and the reason is an interesting one.
Storing more data on a platter requires shrinking the magnetic grains on its surface.
Shrinking the grains below a certain size makes them sensitive to temperature, causing them to randomly flip their orientation.
Using more magnetically resistant materials is possible, but writing data to them requires more energy — and the tiny write head suited to reading from the smaller grains is too small and too weak to generate the magnetic field needed for efficient writing.
The urgent need for storage solutions has driven new and fascinating developments that will soon enable hard disk drives with capacities of up to 140 TB.
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The key technology relies on shrinking the magnetic grains and using a magnetically resistant material. To enable efficient writing, the read head is equipped with a tiny laser that illuminates the target point for a nanosecond at the moment of writing.
The temperature of that spot instantly rises to several hundred degrees, allowing the write head to easily flip its magnetic orientation; immediately afterward, the spot cools and freezes in the newly written magnetic direction.
Another approach involves generating microwave fields that agitate the magnetic grains in place, making them less stable and therefore easier to write to magnetically.
An even more innovative approach changes the structure of the disk entirely.
In this method, the metal platters are replaced with ultra-thin glass plates, allowing more storage platters to be packed into each hard drive.
Metal platters tend to warp when made too thin, but advanced glass retains its shape even at the high temperatures required by the next-generation manufacturing process.
Packing the platters too closely together can cause vibrations, so the interior of the hard drive is filled with helium. Helium is less dense than air, which preserves stability.
This approach introduces a new challenge: how to read data from all the platters efficiently. To solve this, two arrays of read heads are positioned at opposite ends of the drive.
In this configuration they operate in parallel, enabling a significantly higher read/write speed that makes for a worthy alternative to SSD drives.
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The flood of data we generate will only grow as our artificial intelligence tools improve. Fortunately, science and technology are doing their part in the meantime to make that possible.
Shabbat Shalom 😊
In the video: part of the HDD manufacturing process | Credit: Science Channel
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