Hard drive manufacturer Seagate promises that HAMR—Heat Assisted Magnetic Recording—hard drives in 18TB and 20TB models will be available in retail channels in 2020. The new drives use a medium that is less magnetically malleable at standard operating temperature than CMR (Conventional Magnetic Recording) media and, therefore, needs to be briefly and locally heated with a laser as data is written onto the media.
Seagate has been working on HAMR for a long time; the company’s first big press release about the technology came in 2002. The promise has always been the same—higher areal densities, meaning more bits stored per square inch, with higher stability of data once written. The projected densities themselves have increased over the years, though—when Ars Technica first reported on Seagate and HAMR in 2012, the company was promising 6TB HAMR drives were just around the corner.
Although the 2012 “just around the corner” HAMR drives seem to have been mostly vapor, the technology is a reality now. Seagate has been trialing 16TB HAMR drives with select customers for more than a year and claims that the trials have proved that its HAMR drives are “plug and play replacements” for traditional CMR drives, requiring no special care and having no particular poor use cases compared to the drives we’re all used to.
We advise a little bit of caution regarding the claims that the drives are truly “plug and play” replacements. While there’s no indication that HAMR itself has performance implications, many of these drives will also feature SMR—Shingled Magnetic Recording—technology, which already frequently results in drastically reduced write speed when data is not written in large, contiguous sequences. It doesn’t take much searching to find examples of real-world users who have experienced poor performance with non-HAMR SMR drives—such as this Reddit user who reported latencies of 10 full seconds for random I/O loads.
Seagate is not the only vendor with HAMR on the immediate roadmap: hard disk media manufacturer Showa Denko—the largest independent platter manufacturer in the world—announced its own HAMR media technology, which, like Seagate’s, is based on thin films of Fe-Pt (iron and platinum) alloy. Showa Denko claims its HAMR medium will eventually allow for densities of 5Tb/in² or more, making 70-80TB 3.5-inch hard drives possible. Rival hard drive manufacturer Western Digital has been trialing MAMR—Microwave Assisted Magnetic Recording—technology instead, but it has plenty of HAMR patents as well.
The one thing all these vendors agree on is the obsolescence of non-energy-assisted PMR (Perpendicular Magnetic Recording) magnetic recording. PMR densities are currently at about 1.1Tb/in² and are not expected to get much—if any—higher, due to limitations imposed by the Magnetic Recording Trilemma: you need the medium to be resistant to changes in magnetization (for stability), yet your heads need to be able to overcome that resistance in order to write to the medium—and the smaller the individual grains on the medium, the smaller the magnetic field your head can generate to change it without overlap and, therefore, the weaker that field must get.
Listing image by Seagate