Do you still use a device with a mechanical hard drive in it? Flash storage has become so cheap and ubiquitous that outside of backup systems and NAS, SSDs and flash memory now hold the data on most of our devices. Hard drive shipments peaked in 2015, and fewer are sold every year, but in terms of terabytes sold, hard drives are more important than ever. With web storage and backups, we're dumping more of our data into the cloud, and add in AI and big data, and global server capacity is increasing faster than ever.
Flash is making inroads in servers, but physical hard disks still form the backbone of data farms. Larger drives have a lot of advantages for server operators. A bigger disk has greater "areal density" — how much data is stored per square inch — which can improve disk speed, and swapping larger disks into an existing system is almost always cheaper way to boost capacity than builder out new server racks. Disk capacity has continued to grew steadily, but with recent 16TB and 18TB drives, we're approaching the limits of conventional technology.
It works like this. Hard drives store data by changing the polarity of magnetic "bits" on the drive platter. Essentially they write data by changing these bits so magnetic North is pointing either up or down. These bits are arranged into concentric rings called "tracks". You can increase the storage capacity of a hard drive in a few ways: Add more disks (also called "platters"), add more tracks per platter or make the bits smaller (increase the bits per track). Each of these has a few problems, though.
For one, we're just out of space to add platters. An 18TB drive may be cramming nine platters into a standard hard drive enclosure. Adding more bits or tracks have their own problems, too. To make either smaller, you also need to shrink the write head. If the head is too much larger than the tracks or the bits, you're liable to accidentally overwrite neighboring bits when you try to write, like trying to use a giant marker to write on narrow-lined paper.
You can shrink the write head, but this makes it harder to generate the magnetic field needed to write data. You can cope with this by changing the platter material — by lowering its "coercivity" or how resistant it is to outside magnetic fields — but this introduces a new problem. At the scale of nanoparticles, like those on a hard drive, materials with low coercivity have a tendency to randomly flip their magnetic polarity, not good if you want reliable, long-term data storage.
The solution may be two new techniques called microwave and heat-assisted magnetic recording, or MAMR and HAMR. These use an energy source, either a microwave-generating device called a "spin-torque oscillator" or a laser, or change the platter material's coercivity. This, coupled with a more stable platter material and a smaller write head, lets you pack more data onto each platter. Toshiba just shipped the first MAMR drive, an 18TB model, earlier this month, and MAMR drives from Western Digital are expected shortly. Seagate has 20TB drives out to enterprise partners, and we may get consumer versions of those as well.
It's still early days with both these bits of tech, but drives made with these methods (collectively called "energy assisted magnetic recording" or EAMR), should enable drives up to 60TB and possibly beyond. Add other changes like dual-actuator designs that could double read speeds, and hard drives should see huge improvements in the next few years.
For more info on how HAMR and MAMR actually work, along with another technique from Western Digital called EPMR, check out the full video, and see our list of sources here