So they have managed to put 15 TB for the first time on a traditional hard drive

[Blexfraptor]

In October 2017, Western Digital launched the first 14 TB hard drive, which represented a new record in storage capacity. While we are still waiting for units of 16 and 18 TB, which will arrive before 2020, the company has once again broken the record by launching a 15 TB hard drive: the highest capacity in the market.

Western Digital Ultrastar DC HC620: the first 15 TB hard drive
The model in particular is the Ultrastar DC HC620, which is available in two capacities of 14 and 15 TB. Obviously, these types of units are not available to most mortals, but are designed for data centers and servers for the cloud. The key to this type of units is that, in the long term, they offer greater energy efficiency, in addition to requiring less space.

This is the reason why many companies are constantly renewing their storage, changing even hard drives that work to sell them and acquire new ones with their multiple advantages.

To be able to introduce more and more terabytes in the hard disks it has been necessary to go making innovations that allow to increase the density of its interior. Up to 10 TB, most manufacturers use a stacking form called Perpendicular Magnetic Recording, or PMR. From there, it has been necessary to use the so-called Shingled Magnetic Recording, or SMR.

SMR allows increasing the density by stacking the storage in layers, but sacrificing speed of reading and writing on the road. As the main problem we have a slow writing speed, but reading along with other hard drives. This is due to the Read-modify-write mechanism used by these units, which take the information that exists in a site, temporarily store it in a cache while it is being written, and then place it again.

SMR and Helio: the keys of this new 3.5-inch hard drive
The main clients of this type of units are aware that normally very little information is written in these units, and basically what is done most of the time is reading it. In addition, the information is distributed by hundreds of units at a time, so the speed of writing is not a serious problem.

WD has improved this mechanism with this new 15 TB unit, being 31% more efficient than the previous generation of SMR. The maximum transfer speed is 255 MB / s, with 2.5 million guaranteed hours of constant operation, which is equivalent to 285 years in a row. The largest WT unit of 14 TB, the HC530 introduced a few months ago, used PMR, but the company has had to resort to SMR to continue increasing capacity.

In addition, these units are sealed, which favors greater durability to enter less dust that can damage its interior, and allow to enter helium inside instead of air with its HelioSeal technology. Helium is less dense, so it offers less resistance to moving parts inside the hard drive, including the plates themselves. It also generates less vibration and less consumption.