Acoustic Assisted Magnetic Recording is invented

Read an article today about Acoustic Assisted Magnetic Recording (See Oregon State University article Researchers invent “acoustic-assisted magnetic recording”).

Just like heat assisted magnetic recording (HAMR, see our Disk density hits new record… post) which uses laser beams, acoustic assisted magnetic recording (AAMR) uses ultrasound to heat up a spot on media to help it be magnetized.

Why heat up media?

The problems with the extremely dense storage coming out of the labs these days is that the bits are becoming so small that’s it’s increasingly hard to insure that bits close by aren’t being disturbed when a bit is modified. This has led to an interest in shingled writes which we discussed in Sequential only disks and Shingled magnetic recorded disks posts.

But another possibility is to add heat to the process to isolate a bit on magnetic media. In this way a heated bit will be changed while its cooler neighbors are left alone.

I was at the dental hygenist the other day and she was using a new probe which used ultrasound to break up the plaque. In this case, it was also spewing water to cool the tip.  In any event, it appears as if ultrasound can be used to heat up, break stuff and image soft tissue, pretty versatile technology.

Is AAMR better than HAMR?

The nice thing about AAMR is that it can potentially be made with all solid state electronics and as such, wouldn’t require any optical componentry like HAMR.   So in the race against HAMR this could be a crucial edge and thus, could potentially be much easier to fabricate for use in tomorrows disk drives.

I foresee some possible problems with the technology, such as what is size of the heated spot and will the ultrasound emitter need any cooling (like the dental probe).

But it all seems like a reasonable and  logical extension of HAMR technologies being developed in labs today. Also, AAMR could quite probably could make use of the same thermally activated media developed for HAMR applications. Not having to come up with a new media formulation should help it get out of the lab even quicker. That is, if its other problems can be worked out.

In the post on HAMR, it had achieved a Tb/sqin in the lab, as the new media density high watermark.  As far as I could tell from the information published on AAMR, there were no new density records being discussed. However, if AAMR is able to achieve anything close to HAMR densities, we are in for larger capacity disk drives for another decade or so.


Photo Credit: AAMR head assembly by Oregon State University


Disk density hits new record, 1Tb/sqin with HAMR

Seagate has achieved 1Tb/sqin recording (source:
Seagate has achieved 1Tb/sqin recording (source:

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 explained

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.

What’s next?

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.