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HDD: glass plates should allow 20 TB hard disks

Friday, September 8th, 2017 | Gadgets

In the future, 3.5-inch hard disks will be manufactured from a glass substrate to accommodate more than 20 terabytes in one housing. The reported computer base, citing the Japanese daily Nikkei. Even if HDDs are losing importance in the consumer segment, large hard disks are still in demand in the cloud area.

    HDD prototypes with glass plates (Photo: Hoya)

So far, platters with an aluminum substrate are typical for 3.5 inch discs, but glass or ceramics is the preferred material for 1.8 and 2.5 inch HDDs. The virtually only supplier of glass plates is the Japanese company Hoya, of which Western Digital had bought a factory years ago. Glass is relevant because the plates can be thinner due to their stiffness and thus fit more discs into a housing. As a result, the possible capacity of a hard disk increases with the same data density.
HGST, for example, uses eight platters for 12 terabytes in the Helium-filled Ultrastar He12, the HDD uses conventional PMR technology (perpendicular magnetic recording). A model with 14 Terabytes is supposed to work with overlapping tracks (Shingled Magnetic Recording), but the writing speed drops. With twelve plates, as Hoya would like to offer, 18 (PMR) and 21 (SMR) terabytes would be possible in a 3.5-inch housing.

HAMR on glass
A further advantage of glass plates is their higher heat resistance compared to aluminum discs. This is relevant for Heat Assisted Magnetic Recording (HAMR), since the data layer must be heated by laser. The read and write head is also somewhat larger in previous prototypes, which is why thinner plates are again advantageous.
Against glass as a substrate material, the costs are likely to be discussed, but the price is generally rising.


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