Anyone who had been around PCs for long will remember the days when drive capacity was measured in megabytes and people thought that they would never use that much space. Then drives were in gigabytes and people thought the same thing again before the terabyte era came to be. Before HDDs can move into the 20TB range for storage capacity, a new type of substrate for the platters that actually store the data will come into play.
A company called Hoya has a new glass substrate that could be used in 3.5-inch desktop size HDDs to expand storage capacity. Currently glass substrates are used mainly for 2.5-inch mobile HDDs. Today most larger 3.5-inch HDDs use platters with an aluminum substrate. The benefit for glass substrates is more rigidity than aluminum meaning they can be thinner than aluminum platters, thereby allowing more inside the drive leading to higher capacity.
Hoya has prototyped 0.5mm and 0.381mm thick substrates in HDDs able to house 10 and 12 substrates respectively in a 3.5-inch HDD about an inch thick. Right now WD has a 12TB HDD with eight disks inside. If a similar drive using 12 discs and shingled magnetic recording (SMR) method the drive capacity can be increased to 20 TB. SMR tech is able to partially superimpose data-storing tracks on adjacent tracks allowing more data on the drive.
Hoya also notes that another benefit to glass substrate disks in HDDs is that they are crucial for heat assisted magnetic recording (HAMR), which is a tech expected to go mainstream in the future. That tech records data in a minute area that is heated by laser light and to use the tech the substrate needs heat resistance of about 700C. Aluminum substrates can only manage about 200C.
To hit that 20TB capacity the recording density will need to be 1.5Tbits/inch square to 2.5 Tbits/inch square. People in the HDD industry expect to see SSDs limited to data accessed frequently and cold data that doesn’t need to be accessed frequently will be stored on HDDs. The market for glass substrates for 3.5-inch HDDs is expected to boom in the coming months.