Toshiba shows 32TB HDDs with heat-assisted and shingled drives

The 32TB model uses HAMR – heat-assisted magnetic recording – which applies heat via a laser to a very small point on the magnetic surface so that only that very small area is polarised by the head during writes.

The 31TB drive employs MAMR – microwave-assisted magnetic recording – which uses a microwave field to make the area around the write head more susceptible to the magnetism applied to it.

Without this mechanism, the magnetic field of the head – such as on a conventional HDD – is less precise and more extended. This means the data occupies a greater area, with less stored per track, so the total capacity is lower.

The 32TB HAMR drive uses 10 platters, which is the maximum currently possible in a conventional hard drive. The 31TB MAMR drive reaches its capacity by use of 11 platters.

The capacity of each platter on the 31TB drive is 2.8TB, and 3.2TB on the 32TB drive. In total, HAMR technology provides around 15% of the jump in capacity.

SMR also needed to get more capacity

The capacity per platter face on a conventional HDD is a little over 1TB. That means for Toshiba’s drives to achieve the 40% to 45% boost in capacity, they also have to use shingled magnetic recording (SMR) technology, which superposes or overlaps successive data tracks in a pattern that is reminiscent of the way roof tiles overlap.

But SMR hard drives face a particular constraint because it’s not possible to modify the contents of a track without rewriting tracks around it. This means SMR drives are only really useable for data that’s written once-and-for-all, such as backups, archives or documents stored to be read-only.

SMR hard drives are commonly used by hyperscalers for their cold storage services because they have the skills in-house to deal with the constraints faced when dealing with superposed disk tracks. Although there are players that offer storage based on SMR drives, such as Estonian company Leil Storage.

Rainer Kaese, senior manager in business development for storage products at Toshiba Electronics Europe, recently told ComputerWeekly.com in a podcast that he expected hard disk drives to reach 40TB or 50TB in the coming decades, with capacities in the hundreds of terabytes possible but not necessarily able to achieve commercial viability.