Well I thought 36TB on my Mac was going to be enough. Then along comes Seagate with this weeks announcement of reaching 1Tb/sqin (1 Trillion bits per square inch) using their new HAMR (heat assisted magnetic recording) technology.
Current LFF drive technology runs at about 620Gb/sqin providing a 3.5″ drive capacity of around 3TB or about 500Gb/sqin for 2.5″ drives supporting ~750GB. The new 1Tb/sqin drives will easily double these capacities.
But the exciting part is that with the new HAMR or TAR (thermally assisted recording) heads and media, the long term potential is even brighter. This new technology should be capable of 5 to 10Tb/sqin which means 3.5″ drives of 30 to 60TB and 2.5″ drives of 10 t0 20TB.
HAMR uses both lasers and magnetic heads to record data in even smaller spaces than current PMR (perpendicular magnetic recording) or vertical recording heads do today. You may recall that PMR was introduced in 2006 and now, just 6 years later we are already seeing the next generation head and media technologies in labs.
Denser disks requires smaller bits and with smaller bits disk technology runs into three problems readability, writeability and stability, AKA the magnetic recording trilemma. Smaller bits require better stability, but better stability makes it much harder to write or change a bits magnetic orientation. Enter the laser in HAMR, with laser heating the bits can become much more maleable. These warmed bits can be more easily written bypassing the stability-writeability problem, at least for now.
However, just as in any big technology transition there are other competing ideas with the potential to win out. One possibility we have discussed previously is shingled writes using bit patterned media (see my Sequential only disk post) but this requires a rethinking/re-architecting of disk storage. As such, at best it’s an offshoot of today’s disk technology and at worst, it’s a slight detour on the overall technology roadmap.
Of course PMR is not going away any time soon. Other vendors (and proboblf Seagate) will continue to push PMR technology as far as it can go. After all, it’s a proven technology, inside millions of spinning disks today. But, according to Seagate, it can achieve 1Tb/sqin but go no further.
So when can I get HAMR disks
There was no mention in the press release as to when HAMR disks would be made available to the general public, but typically the drive industry has been doubling densities every 18 to 24 months. Assuming they continue this trend across a head/media technology transition like HAMR, we should have those 6GB hard disk drives sometime around 2014, if not sooner.
HAMR technology will likely make it’s first appearance in 72oorpm drives. Bigger capacities seem to always first come out in slower performing disks (see my Disk trends, revisited post)
HAMR performance wasn’t discussed in the Seagate press release, but with 2Mb per linear track inch and 15Krpm disk drives, the transfer rates would seem to need to be on the order of at least 850MB/sec at the OD (outer diameter) for read data transfers.
How quickly HAMR heads can write data is another matter. The fact that the laser heats the media before the magnetic head can write it seems to call for a magnetic-plus-optical head contraption where the laser is in front of the magnetics (see picture above).
How long it takes to heat the media to enable magnetization is one critical question in write performance. But this could potential be mitigated by the strength of the laser pulse and how far the laser has to be in front of the recording head.
With all this talk of writing, there hasn’t been lots of discussion on read heads. I guess everyone’s assuming the current PMR read heads will do the trick, with a significant speed up of course, to handle the higher linear densities.
As for what comes after HAMR, checkout another post I did on using lasers to magnetize (write) data (see Magnetic storage using lasers alone). The advantage of this new “laser-only” technology was a significant speed up in transfer speeds. It seems to me that HAMR could easily be an intermediate step on the path to laser-only recording having both laser optics and magnetic recording/reading heads in one assembly.
Lets see 6TB in 2014, 12TB in 2016 and 24TB in 2018, maybe I won’t need that WD Thunderbolt drive string as quickly as I thought.