Seagate’s areal density roadmap

Lots and lots of capacity headroom

Seagate is currently in its second generation of perpendicular magnetic recording (PMR) technology. This technology has a way to go and will be followed, Seagate believes, by two other technologies leading to more than 10 terabits of information per square inch of disk drive recording media.

The 3-step area density improvement road map comes from a Seagate presentation to analysts in September last year by Dave Wickersham, the company’s President and COO, and looks like this:-

1. PMR – This technology could be pushed forward and take us to the 1 terabit/square inch area. Wickersam thinks that it will enable the provision of 1.5TB per 3.5-inch platter. In September last year Seagate was shipping roughly 200GB/platter, so a 7X improvement is being looked at with the result being a 4.5TB, 3-platter drive and a 3TB 2-platter drive. Seagate currently has not shipped a 1TB 3.5-inch drive although one is expected shortly

2. HAMR or heat-assisted magnetic recording involves heating a tiny, tiny portion of the media surface, smaller than a PMR element, changing its magnetic polarity and then cooling it to seal in the signal. Seagate thinks it could attain 10Tbit/sq in with this technology. In that case a 3.5-inch HAMR disk could run from a 1.5TB/platter up to a 15TB/platter as the areal density improves from 1Tbit/sq in to 10Tbit/sq in.

That means 2 and 3-platter HAMR drives could offer from 3TB to 30TB and from 4.4TB to 45TB respectively. These seemingly amazing capacities are several years away from volume production which would start at the lower level and take several years to reach the upper levels.

3. Bit pattern media or BPM involves extremely small islands of magnetic elements surrounded by insulating material, thus poviding a sharper signal for read heads with less distracting noise. This could achieve approximately the same areal density as HAMR. By combining HAMR with BPM Seagate reckons it could go well beyond 10Tbit/sq in but doesn’t provide example numbers.

Let’s assume there is a 50 percent increase as a result and that a 15Tbit/sq in areal density is achievable. This would mean a 3.5-inch platter could hold 22.5TB and a 2-platter drive would offer up to 45TB with a 3-platter drive topping out at 67.5TB.

It’s possible that the I/O bandwidth available would encourage people to use smaller 2.5-inch drives as the streaming of large files, very, very large files, onto or off (for backup) such massively capacious 3.5-inch drives could take a relative age.

What about timeframes?

2012 – PMR limit of 1Tbit/sq in reached
2017 – HAMR or BPM limit of 10Tbit/sq in reached or HAMR/BPM combo of 10+Tbit/sq in attained.

These dates are of course, very speculative.


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