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PMR Type 2

by Administrator on July 22, 2010

I hadn’t heard of this before a few days ago, when I was fact checking some of the info on Fujifilm’s video interview around its breakthrough with IBM in tape capacity.  I had thought that the IBM-Fujifilm tape capacity demonstration showed the application of PMR head technology to a new tape coating that used BaFe particles to achieve the great density improvement.  (Disk technology has been borrowed repeatedly by the tape guys in density improvement.) 

Anyway, in the video review process, Rich Gadomski at Fujifilm deleted all of our crawls on the video (text appearing under the speaker as he talks) that referenced Perpendicular Magnetic Recording heads.  He said that the demo used standard GMR heads only.

Was I wrong?  Had to find out.  So, I contacted IBM.  Here is the email exchange:

Hi Jon,

thanks for your request.

In fact it is a joint release and joint work with Fujjifilm. You find the press announcement here:

Regarding your second question, I am in contact with the project leader. Expect an answer tomorrow.

For which trade media are you writing? Are you usually covering storage topics? Let me know if you want to be informed about further milestones in this area and/or other areas of your interest in which we have acitvities.

Best regards,

Nicole Herfurth
Communications/Media Relations
IBM Research — Zurich

Nicole gave the question to the brainiacs at IBM who worked on the demo.  She got back to me with this.

Evangelos Eleftheriou, Storage research leader at IBM Research – Zürich, confirmed:
For the 29.5 Gbit/in2 demo we used flexible tape media based on ultra-fine, perpendicularly-oriented BaFe particles.

Please also note, that we’ve demonstrated 29.5 Gbit/in2 which would enable cartridge capacities that could hold up to 35 trillion bytes (terabytes) of uncompressed data.

Just to be sure that nothing was being lost in translation, I emailed her again.

Thanks again for the response. But, I am not sure if I am communicating or understanding properly here.

I know that BaFe media presents perpendicularly-oriented particles. Does that mean that PMR approaches are used to write data to the media? Isn’t a PMR head simply a modified GMR head? That still isn’t coming through to me.

Tape has, over the past couple of years, improved capacity in part by “borrowing” head technology developed for disk drives. GMR heads are an example — they were developed in the disk world, then ported to tape. A couple of years ago, when parallel recording was facing a superparamagnetic limit that would restrict disk recording density, perpendicular recording was introduced. That technology seems to have been ported to tape now, with this development, yielding dramatic tape density improvement as well. Am I correct in this assumption?

Secondly, is there an outside theoretical limit to the density achievable with this new tape technology? Cartridge capacities start at 35TB. Where do they max out? With disks, the theoretical limit of density enabled by PMR is placed at 800Gb per square inch. That seems to be the reason for introducing new bit patterned media, which promises a next gen disk drive of 40+ TB on a 2.5inch drive. Do we know what the limit is on this technology with respect to tape density? Is there another generation in the wings?

Lots of questions, the first being the most important.

She followed up with another ping of her scientist, inadvertantly copying me on her email to him — which I include here because it is a gem of a statement itself and provides great insight into the view of the blogosphere and IT trade press writers generally held by most vendors:

Hi Evangelos,

I guess I have to ask you again to take a look at the journalist’s request. At least he really tries to be correct.

Best regards,

Well, I try to be accurate.  Anyway, here was the answer.

Hi Jon,

It took a while but here is an answer from Evangelos to your questions:

1. Fujifilm has manufacured media based on ultra-fine perpendicularly, longitudinally, or randomly -oriented BaFe particles.

2. For the demo we used perpendicularly-oriented BaFe media with standard write/read head technology. I should emphasize that the perpendicularly-oriented BaFe medium does not support “soft underlayer” as in PMR recording for HDDs. In HDD PMR this magnetically soft underlayer is essential and can be effectively considered as part of the write head (which in the case of “real” PMR is a monopole), making the write head more efficient. However, in our demo the perpendicular orientation of the BaFe particles still gave a substantial boost in SNR performance. This type of recording is some times called type 2 PMR.

3. It is correct that the tape industry follows the developments of the HDD industry regarding head technology. GMR read sensors were introduced by some vendors in tape drive systems only 3 to 4 years ago.

4. In the magnetic recording industry there have always been limits that turn out to be wrong. I wouldn’t risk quoting an areal recording limit for tape because such a limit depends on many different things. I could only mention that for “particulate” flexible tape media 100 Gbit/in2 might be possible. Remains to be seen!

Can you tell us when your article/video goes live?

Sure will, Nicole.  It will post shortly. 

So, Type 2 PMR emerges.  It uses the perpendicular orientation properties of the media coating itself, rather than a specialty head, to align bit magnetic fields perpendicularly on the media.

Your moment of geek for the day.

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