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Seagate REJECTED buyout offer for Virident – analyst

Go ahead, WD, pay half a billion for it... we have some top secret tech to get on with

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Hard drive supremos Seagate had first refusal on buying out enterprise flash startup Virident – and turned it down, leaving WD free to snap it up for $685m.

This little bombshell burst forth from a report on a Seagate Analyst Day by Stifel Nicolaus' chief, Aaron Rakers. A second juicy nugget was that Rakers thinks there were other bidders as well as WD for Virident.

Rakers' report contained yet another storage revelation on top of those two: Seagate are adopting a little-known disk drive recording technology called Two Dimensional Magnetic Recording (TDMR).

Seagate will also, says Rakers, ship a 3D NAND SAS-interface SSD in the first half of 2014. El Reg's storage desk believes this will use Samsung 3D V-NAND chippery.

Just to put the cherry on that nicely iced cake, Seagate is developing two enterprise SSD controllers internally.

TDMR

Seagate sees hard disk drive recording technology having an intermediate Two Dimensional Magnetic Recording (TDMR) technology being used soon, before moving to HAMR (Heat-Assisted Magnetic Recording). TDMR sounds like a stop-gap, similar to shingling (SMR), as it will only produce a 20 per cent or so increase in areal density over SMR.

The company said nothing at all about TDMR when it introduced shingling and HAMR to journalists at a briefing in August. It says HAMR product integration could start in 2016, by which time TDMR product integration would be under way.

TDMR "involves improved signal-to-noise ratio" according to Rakers. Searching for TDMR info on Seagate's website gets you zip, nada, nothing – at the time of writing, anyway.

Googling "Two Dimensional Magnetic Recording" gets you lots of papers from data recording conferences. An HGST one (PDF, 59 pages), for a presentation in October 2010 to the IEEE Magnetics Society's Santa Clara Chapter, positions TDMR as an associated technology for shingling.

It states:

  • Two-Dimensional Magnetic Recording (TDMR) = Shingled Write + 2D Readback
  • Two-Dimensional Readback implies either several revs of latency, or a read head with three or more immediately adjacent sensor elements.
  • In 2D-readback, a complete ‘picture’ is built up from multiple tracks - ITI (Inter-Track Interference) is no longer destructive. ITI contains information about the data that powerful detectors can extract
TDMR diagram

TDMR diagram. (Y. Shiroishi, Intermag 2009, FA-01)

TDMR is an extension of shingling technology. The 2-dimensionality comes from the read signal information being stored along the track - dimension 1 - and across tracks, along the radius of the disk - dimension 2. This, you would think, would slow writing in the same way as shingling does, but researchers suggest flash-based caching and buffering could counteract that.

It seems to the storage desk at El Reg that it is the combination of SMR and TDMR that is Seagate's response to HGST's helium-filled drives, which have more platters and heads than air-filled drives.

Seagate reckons SMR could generate a 20TB HDD with a 1.2Tbit/in2 areal density. HAMR could produce up to 5Tbit/in2 areal density; that's the big jump that will enable HDDs to regain some sort of parity between their capacity growth and data storage growth. ®

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