Two-Dimensional Magnetic Recording Due in 2017

Two-dimensional magnetic recording (TDMR) is a yet another technology that should help to increase areal density and this is something that Seagate is investing in. The manufacturer believes that TDMR helps to increase areal density by 5% to 10%. Plans were announced several months ago and during the conversation with Mark Re, it was confirmed that Seagate was on track to release its first commercial TDMR-based HDDs in 2017.

TDMR technology enables makers of hard drives to increase the areal density of HDD platters by making tracks narrower and pitches even smaller than they are today. While it is possible to minimize the writer (a part of an HDD's head that writes data), reading becomes a challenge. As magnetic tracks become narrower, they start to affect each other, an effect called magnetic inter-track interference (ITI). This means It becomes increasingly hard for HDD heads (readers) to perform read operations. To mitigate the ITI effect of very narrow tracks, two-dimensional magnetic recording technology uses an array of heads to read data from either one, or several nearby tracks (a method described in several scientific publications). This improves the signal-to-noise ratio delivered to the controller. Several readers enable HDD controllers to determine the correct data based on input from several locations, which implies the need for powerful controllers. More importantly, a number of read heads will be a benefit for HDDs featuring HAMR in the future: heat-assisted recording improves the write process, whereas multiple readers improve the read process. We are also told that with relevant programming, hard drives featuring an array of readers per head can increase the performance of HDDs. This will clearly not make the new hard drives as fast as SSDs, but it will help Seagate’s customers (particularly in the SAS space) to increase the performance of their storage devices. Right now, Seagate does not talk about its plans to use multiple readers in commercial drives because such products are several years out, but considers this a possibility.

Seagate confirmed that TDMR lets HDD makers to increase areal density by up to 10%, which is a noticeable amount compared to typical PMR platters. However, additional capacity does not come free in this case when it comes to computing. An array of heads increases bandwidth requirements for the controller as well as the amount of information that the chip needs to process. As a result, the whole TDMR platform becomes generally expensive: it features multiple arrays of heads, new platters, new motors as well as new controllers. This is why Seagate plans to use it for server applications first sometime in early 2017. Seagate did not confirm whether such HDDs would use both TDMR and helium, but said that virtually all technologies could be mixed and matched to build the right solution for every possible application. Keep in mind that these are plans which are subject to change.

Helium Will Remain Exclusive for High-Capacity Applications, For Now New 10K and 15K RPM HDDs Incoming
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  • Notmyusualid - Wednesday, July 6, 2016 - link

    Just lost my Seagate 4TB 2.5" internal disk last week.

    Luckily my most precious things were backed-up elsewhere, but dam, 2.4TB lost.
  • jwcalla - Thursday, July 7, 2016 - link

    I'm honestly fed up with the poor reliability of HDDs. Of the three ones I still had in service, two are dead, and I'll never buy those two brands again.
  • Michael Bay - Thursday, July 7, 2016 - link

    Out of not so idle interest, what were they?
  • kamm2 - Thursday, July 7, 2016 - link

    This was in the back of my mind the whole time I read this article. What good is any of this if the damn drives keep dying? Maybe things are different on the enterprise side but I've given up on Seagate drives.
  • jbrizz - Wednesday, July 6, 2016 - link

    Can we just have 5.25 inch hard drives again? I don't care so much about density at home, but I need to hoard more files!
  • rstuart - Wednesday, July 6, 2016 - link

    I like most have move to use SSD exclusively for the, hmm, "boot drive", But I do use HDD's for media storage where only the biggest highest density drive works. SSD's are currently about an order of magnitude more expensive per byte in this area. At a wild guess SSD's might reach price parity in a decade, but for now the HDD's are the only sane choice.

    I'm currently struggling to fit in 6TB. My guess is 10Tb would be enough for the foreseeable future, and 20Tb would cover everything I am every likely to need. So I rather pleased to see Mr Re say they will hit 20Tb in a few years.
  • patrickjp93 - Wednesday, July 6, 2016 - link

    Samsung is hitting 15TB this year, so Seagate is done in enterprise. The performance/watt/$ is just vastly superior for SSDs. Once storage density is also in the wheelhouse of SSDs, the scales will tip and never go back.
  • gospadin - Thursday, July 7, 2016 - link

    absolute density (TB/m3) is already in SSD's advantage

    The biggest 2.5" HDD you can buy today is 2TB. In that form factor, Samsung is currently selling 4TB SSD, with 8TB/16TB drives announced.
  • Lolimaster - Friday, July 8, 2016 - link

    Do like me:

    4x6TB WD blues, so should be covers for some time.
  • anactoraaron - Thursday, July 7, 2016 - link

    This paragraph was enlightening -
    HDDs that use shingled recording write new tracks that overlap part of the previously written magnetic tracks. The overlapping tracks may slow down writing because the architecture requires HDDs to write the new data and then rewrite nearby tracks as well.

    Which explains why my 5tb seagate with this tech can't seem to get past 40MB/s when writing to the drive.

    Then read this - Ultimately, environments that involve a decent amount of writing might not be impressed with SMR performance, but the key figure here is density.

    Is anyone getting a high capacity drive going to be impressed with 2-40 MB/s?

    No. No they will not.

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