Do you still use a device with a mechanical hard drive? Flash storage has become so cheap and ubiquitous that, outside of backup systems and NAS, SSDs and flash memory now store data on most of our devices. Hard drive shipments peaked in 2015 and less are sold each year, but in terms of terabytes sold, hard drives are more important than ever. With web storage and backups, we’re pouring more data into the cloud and adding AI and big data, and the global server capacity is increasing faster than ever.
Flash is making inroads on servers, but physical hard drives still form the backbone of data farms. Larger units have many advantages for server operators. A larger disk has a higher “area density” – how much data is stored per square inch – which can improve disk speed, and swapping larger disks in an existing system is almost always a cheaper way to increase capacity than to build new server racks. Disk capacity has continued to grow steadily, but with the recent 16 TB and 18 TB drives, we are approaching the limits of conventional technology.
It works like that. Hard drives store data by changing the polarity of the magnetic “bits” on the drive plate. Essentially, they write data by changing these bits so that the magnetic north is pointing up or down. These bits are organized in concentric rings called “tracks”. You can increase the storage capacity of a hard drive in a few ways: Add more discs (also called “platters”), add more tracks per plate, or make the bits smaller (increase the bits per track). Each of them has some problems, however.
On the one hand, we are out of space to add dishes. An 18 TB drive may be full nine dishes in a standard hard drive enclosure. Adding more bits or tracks also has its own problems. To make them smaller, you also need to shrink the recording head. If the head is much larger than the tracks or bits, you are liable to accidentally overwrite neighboring bits when trying to write, such as trying to use a giant marker to write on thin line paper.
You can reduce the recording head, but this makes it more difficult to generate the magnetic field needed to record data. You can deal with this by changing the material on the plate – decreasing its “coercivity” or its resistance to external magnetic fields – but this presents a new problem. On the scale of nanoparticles, like those on a hard disk, materials with low coercivity tend to randomly change their magnetic polarity, which is 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. They use a power source, a microwave generating device called a “rotation torque oscillator” or a laser, or they alter the coercivity of the plate material. This, together with a more stable cymbal material and a smaller recording head, allows you to package more data on each cymbal. Toshiba has just launched the first MAMR drive, an 18 TB model, earlier this month, and Western Digital MAMR drives are expected soon. Seagate offers 20 TB disks to corporate partners and we can also obtain consumer versions of them.
It is still the beginning with these bits of technology, but drives made with these methods (collectively called “energy-assisted magnetic recording” or EAMR), should allow drives up to 60 TB and possibly beyond. Add other changes, such as dual actuator designs that can double reading speeds, and hard drives are expected to see major improvements in the years to come.
For more information on how HAMR and MAMR really work, along with another Western Digital technique called EPMR, check out the full video and see our list of sources here