Using a glass substrate instead of aluminum [digitaltrends.com] could allow 12 platters to be crammed into a 3.5" hard disk drive enclosure:
Even if many modern systems eschew classic hard drive storage designs in favor of solid state alternatives, there are still a number of companies working on improving the technology. One of those is Hoya, which is currently prototyping glass substrates for hard drive platters of the future which could enable the production of drives with as much as 20TB of storage space.
Hard drive platters are traditionally produced using aluminum substrates. While these substrates have enabled many modern advances in hard drive technology, glass substrates can be made with similar densities, but can be much thinner, leading to higher capacity storage drives. Hoya has already managed the creation of substrates as thin as 0.381mm, which is close to half the thickness of existing high-density drives.
In one cited example, an existing 12-terabyte drive [hgst.com] from Western Digital was made up of eight platters. Hoya believes that by decreasing the thickness of the platters through its glass technology, it could fit as many as 12 inside a 3.5 inch hard drive casing. That would enable up to 18TB of storage space in a single drive (thanks Nikkei [nikkeibp.co.jp]).
When that is blended with a technology known as "shingled magnetic recording [nikkeibp.co.jp]," 20TB should be perfectly achievable.
Toshiba is reportedly planning to release a 14 TB helium-filled hard drive [hothardware.com] by the end of the year.
Also at Network World [networkworld.com].