Hard disk makers are using capacity as their chief bulwark against the rise of solid-state drives (SSDs), since they certainly can\u2019t argue on performance, and Western Digital \u2014 the king of the hard drive vendors \u2014 has shown off a new technology that could lead to 40TB drives.\nWestern Digital already has the largest-capacity drive on the market. It recently introduced a 14TB drive, filled with helium to reduce drag on the spinning platters. But thanks to a new technology called microwave-assisted magnetic recording (MAMR), the company hopes to reach 40TB by 2025. The company promised engineering samples of drive by mid-2018.\n\nMAMR technology is a new method of cramming more data onto the disk. Western Digital\u2019s chief rival, Seagate, is working on a competitive product called HAMR, or heat-assisted magnetic recording. I\u2019ll leave it to propeller heads like AnandTech to explain the electrical engineering of it all. What matters to the end user is that it should ship sometime in 2019, and that\u2019s after 13 years of research and development.\u00a0\nThat\u2019s right, MAMR was first developed by a Carnegie Mellon professor in 2006 and work has gone on ever since.\nThe physics of hard drives\nJust like semiconductors, hard drives are running into a brick wall called the laws of physics. Every year it gets harder and harder to shrink these devices while cramming more in them at the same time.\nWestern Digital believes MAMR should enable 15 percent decline in terabytes per dollar, another argument hard disk has on SSD. A hard disk will always be cheaper per terabyte than SSD because cramming more data into the same space is easier, relatively speaking, for hard drives than flash memory chips. MAMR and HAMR are expected to enable drive makers to pack as much as 4 terabits per square inch on a platter, well beyond the 1.1 terabits per square inch in today\u2019s drives.\nData growing faster than hard disk capacity\nThe thing is, data is growing faster than hard disk capacity. According to research from IDC (sponsored by Seagate, it should be noted), by 2025 the global datasphere will grow to 163 zettabytes (a zettabyte is a trillion gigabytes). That\u2019s 10 times the 16.1ZB of data generated in 2016. Much of it will come from Big Data and analytics, especially the Internet of Things (IoT), where sensor data will be picking up gigabytes of data per second.\nAnd those data sets are so massive, many companies don\u2019t use them all. They dump their accumulated data into what are called data lakes to be processed later, if ever. I\u2019ve seen estimates that collected data is unused as high as 90 percent. But it has to sit somewhere, and that\u2019s on a hard disk.\u00a0\nMind you, that\u2019s just Big Data. Individuals are generating massive quantities of data as well. Online backup and storage vendor BackBlaze, which has seen its profile rise after it began reporting on hard drive failures, uses hundreds of thousands of drives in its data centers. It just placed an order for 100 petabytes worth of disk storage, and it plans to deploy all of it in the fourth quarter of this year. And it has plans for another massive order for Q1. And that\u2019s just one online storage vendor among dozens.\u00a0\nAll of that is great news for Western Digital, Seagate and Toshiba \u2014 and the sales reps who work on commission.