Are you still using a device with a mechanical hard drive in it? Flash storage has become so cheap and ubiquitous that outside of the backup systems and NAS, SSDs and flash memory contains the data on most of our devices. Hard drive delivery peaked in 2015, with fewer sales each year, but in terms of terabytes being sold, hard drives are more important than ever. With web storage and backup, we dump more of our data into the cloud, add our AI and big data, and global server capacity increases faster than ever.
Flash is entering servers, but physical hard drives are still the backbone of data farms. Larger drives have many benefits for server operators. A larger disk has a larger “surface density” – how much data is stored per square inch – that can improve disk speed, and swapping larger disks into an existing system is almost always a cheaper way to increase capacity than to build new server racks. Disk capacity is constantly growing, but with recent 16TB and 18TB drives we are approaching the limits of conventional technology.
It works that way. Hard disks store data by changing the polarity of magnetic “bits” on the disk. In essence, they write data by changing these bits so that the magnetic North points up or down. These pieces are arranged in concentric rings called ‘spores’. You can increase the storage capacity of a hard drive in several ways: add more slices (also called ‘platters’), add more cuts per dish or make the pieces smaller (increase the pieces per cut). However, all of these issues have some issues.
First, we just no longer have space to add plates. An 18TB drive can be jam-packed nine paste into a standard hard disk drive. Adding more pieces or cuts also has their own problems. To get smaller, you also need to shrink the writing head. If the head is too much larger than the traces or pieces, you may accidentally overwrite neighboring pieces when trying to write, such as using a giant marker to write on narrow paper.
You can shrink the write head, but it makes it harder to generate the magnetic field needed to write data. You can deal with it by changing the dish material – by lowering its “compulsion” or how resistant it is to magnetic fields, but this leads to a new problem. On the scale of nanoparticles, such as those on a hard disk, low coercive materials tend to randomly reverse their magnetic polarity, not good if you want reliable long-term storage.
The solution could be two new techniques called the microwave and magnetic recording, or MAMR and HAMR. It uses an energy source, either a microwave-generating device called a ‘torque-oscillator’, or a laser, or changes the constraint of the dish material. This, coupled with a more stable dish material and a smaller writing head, lets you pack more data on each dish. Toshiba has just shipped the first MAMR disk, an 18TB model, earlier this month, and Western Digital MAMR disks are expected soon. Seagate has 20 TB trips to enterprise partners, and we can also get consumer versions of it.
It’s still early days with both pieces of technology, but drives using these methods (collectively called “energy-assisted magnetic recording” or EAMR) should enable drives up to 60 TB and possibly further. Add other changes, such as two-actuator designs that can double read speeds, and hard drives will see major improvements in the next few years.
For more information on how HAMR and MAMR work, along with another Western Digital technique called EPMR, watch the full video and see our list of resources here