Seagate masters 6.9 TB platters and prepares to release a 55 TB HDD

One of the leading HDD manufacturers, Seagate, has managed to develop platters with an impressive 6.9 TB density.
This means that an 8-platter HDD can now reach a total capacity of 55 TB!

Eight-platter drives have existed for quite some time, which is already an achievement on its own.
However, creating a drive with such enormous capacity required the use of HAMR (Heat-Assisted Magnetic Recording) technology.

The idea behind HAMR is to locally heat a tiny area of the disk with a miniature laser right before writing, making the heated surface easier to magnetize.
This speeds up the writing process and allows data cells to be made smaller — ultimately increasing storage density.
The technology itself isn’t new and has been used before, but HDDs were previously capped at around 28 TB.

As we can see, the recording density has effectively doubled! Which means HAMR alone wasn’t enough — additional improvements had to be introduced.

It’s also worth considering that linear read speed doesn’t grow linearly with data density, but rather with the square root of it.
So a doubling in density yields a ~41% increase in speed.
Given that previous-generation drives reached around 270 MB/s, the new models could hit up to 400 MB/s!
Of course, this still can’t compete with SSDs or, especially, NVMe drives—but it’s respectable progress.
And SATA3 remains sufficient, since it provides up to 550 MB/s and won’t become a bottleneck.

The upcoming drives will likely be marketed as Seagate Exos 55TB, possibly carrying the model label
ST55000NM000C — 3.5″ HDD, SATA 6 Gb/s, 7200 RPM, 512 MB cache or maybe even
1024 MB / 1 GB cache. But for now, that’s only speculation.

The primary use case will be storing large datasets, such as AI/ML training databases, where constant random access is not required.
Reliability should remain within acceptable limits, since even if the HAMR laser fails, only writing becomes impossible —
reading the data should still work.

Assuming HDDs don’t experience the same price surge as RAM recently did, the Seagate Exos 55TB will likely cost around €700++.

This also implies the upcoming appearance of cheaper “cold storage” consumer drives in 6 TB and 12 TB capacities, using one or two of the new platters.

As for when the 55 TB Seagate Exos HDD will hit the market, that remains unknown.
Most likely — late 2026.