back to article Seagate finds sets of two heads are cheaper than one in its new and very fast MACH.2 dual-actuator hard disks

For about three years, disk-making giant Seagate has been talking up tech called “MACH.2” – a conventional disk drive that offers considerable speed improvements. And now the disk giant has found that the tech also cuts its costs, raising the prospect that big, fast, hard disk drives might emerge at keen prices. MACH.2 gets …

  1. stungebag

    Is this new?

    I don't get this. When I had an HP disk storage system to worry about all of the (rather expensive) drives claimed to have dual activators. What's different about these Seagates?

    1. CrackedNoggin

      Re: Is this new?

      I searched for a link couldn't find it. Can you?

      WD has been developing 2-actuator in competition with Seagate since at least 2019:

      "Western Digital to Demo Dual-Actuator HDDs Next Week: Double the Actuators for Double the Perf", Anandtech, March 2019.

    2. Anonymous Coward
      Anonymous Coward

      Re: Is this new?

      I believe you are thinking of enterprise dual ported drives. A different thing.

    3. Bubba Von Braun

      Re: Is this new?

      No not new at all.. had to think back to my NCR days, but Conner Peripherals "Chinook" drives. 3.5" SCSI more high throughput than capacity though.

      It seems Seagate has resurrected/perfected the technology as they eventually bought Conner. Will be interesting to see what arrangement they have to interleave the data to get the additional capacity in the same surface area.

      1. Alan Brown Silver badge

        Re: Is this new?

        Chinook had 2 sets of heads on each platter

        This sticks with one head per platter, and is essentially stacking 2 HDDs in one case

        heads in an assembly are accessed individually, not in parallel, because thermal (and other) effects mean that calibration will almost always be out if parallel access is attempted. The only way to allow 2 heads in the stack to be active is to have them pivoting independently (ie: two voice coil actuators, etc) and the complexity is hideous whether you do it with two independent head assemblies on each side of the platters (Chinook) or have two mechanically separated head assemblies on the same pivot

        Whilst Seagate et al ate putting a brave face on it, SSDs have been taking their lunchboxes away for quite a while. They shut down their main research labs a decade back and HAMR/.MAMR is taking a long time to bring the holy grail of reliably increased density, whilst the shenanigans in the wake of the 2011 Thai floods convinced a lot of buyers that getting away from mechanical drives (supply choke points and opportunistic profiteering vendors) was a worthwhile pursuit - last year's shenanigans with submarined prosumer drives being slipped into NAS channels didn't help their cause..

        As much as they talk up these capacities, Soiid state is closing beat them on longevity/endurance a long time ago and is closing rapidly in on mechanical device cost at all densities and a lot of buyers are minded not to reward past bad behaviour by actively avoiding by giving HDD vendors their SSD purchases

        1. captain veg Silver badge

          Re: Is this new?

          I'm a Luddite, but it's solid state all the way even for me when it comes to secondary storage, if only for the noise reduction.

          Backup is a different matter.


  2. Anonymous Coward
    Anonymous Coward

    I was wondering why moving from "1" to "2" took so long, or what else was involved that made that step suddenly worthwhile. Read "Tom's hardware" analysis, it seems that "As hard drive capacity grew further ... random read/write IOPS-per-TB performance dropped beyond comfortable levels for data centers".

    So 2 actuators allows for higher capacity drives without sacrificing random read/write IOPS performance.

    Here is the relevant section quoted

    > Historically, HDD makers focused on capacity and performance: every new generation brought higher capacity and slightly increased performance. When the nearline HDD category emerged a little more than a decade ago, hard drive makers added power consumption to their focus as tens of thousands of HDDs per data center consumed loads of power, and it became an important factor for companies like AWS, Google, and Facebook.

    > As hard drive capacity grew further, it turned out that while normal performance increments brought by each new generation were still there, random read/write IOPS-per-TB performance dropped beyond comfortable levels for data centers and their quality-of-service (QoS) requirements. That's when data centers started mitigating HDD random IOPS-per-TB performance with various caching mechanisms and even limiting HDD capacities.

    > In a bid to keep hard drives competitive, their manufacturers have to continuously increase capacity, increase or maintain sequential read/write performance, increase or maintain random read/write IOPS-pet-TB performance, and keep power consumption in check. A relatively straightforward way to improve the performance of an HDD is to use more than one actuator with read/write heads, as this can instantly double both sequential and random read/write speeds of a drive.

    1. TVC

      I remember fixed head disks.

      Nothing new.

      I remember using disks with one set of heads per track.

      Bloody huge though. Seem to remember seeing one that must have been over a metre across.

      1. Anonymous Coward
        Anonymous Coward

        Re: I remember fixed head disks.

        Any day now someone will reinvent drum storage.

        1. Anonymous South African Coward Silver badge

          Re: I remember fixed head disks.

          Bada-bum-tsss to follow soon...

    2. Phil O'Sophical Silver badge

      Not new

      Using ordinary drives in a RAID enclosure can also do that, at least for READ operations. The controller parallelizes read requests, distributing them around the disks, and using whichever disk has the heads in the best place for a particular request, that's been around since the 1980s at least. Looks like the Seagate solution is just to put this in one drive box & call it a single disk.

      1. Anonymous Coward
        Anonymous Coward

        Re: Not new

        Only on RAID 1 or 10. Not similar at all.

        1. Anonymous Coward
          Anonymous Coward

          Re: Not new

          It's basically RAID0. Two standard 10TB hard drives in RAID0 should perform about the same as one 20TB dual-actuator drive.

      2. Martin Gregorie

        Re: Not new

        ICL were doing something similar back in 1973 when a 60MB removable disk was a big deal, but it was a software, rather than a hardware, solution.

        Their improvement was to maintain two ordered request queues per drive plus a vector showing where the heads were and which direction they were moving. Requests that could be satisfied by keeping the heads moving in the same direction went on one queue and the rest went on the other. The queue pointers were swapped when the 'ahead' queue was emptied.

        This made the heads float gently in and out rather than banging madly back and forth across it. The result was roughly doubled throughput and reduced wear and tear on the drive mechanics. It was a standard feature of the George 3 operating system from, IIRC, Mk 6.4 onward.

        I can't see any reason why something like this couldn't be implemented within the disk drive: the extra queue storage would be relatively minimal and modern disks already contain a microcontroller.

        1. Gene Cash Silver badge

          Re: Not new

          That was called the "elevator" algorithm, and I believe several UNIXes used it as well, which is where I first encountered it.

          1. Crypto Monad

            Re: Not new

            All modern hard drives do this.

            You have a queue of outstanding requests on the bus (SATA/SAS etc). The drive optimises its seek path across the platters, using its knowledge of the rotational positioning of sectors as well as elevator seeking.

            The more parallel I/O you're doing - i.e. the deeper the queue - the more opportunity it has to improve the total throughput.

        2. Anonymous Coward
          Anonymous Coward

          Re: Not new

          Didn't ICL also do CAFS (Content Addressable Filestore) where the disk head had enough "intelligence" that the main CPUs could offload search criteria so the disk only returned a more interesting portion of the data?

          I think we had to reformat the IDMSX database for it to work but it was pretty useful in its time. I wonder if something similar in spirit could be done today.

  3. gnasher729 Silver badge

    Reduced testing time

    That's absolutely brilliant. The drive runs faster, therefore it can be completely tested faster, therefore production time and cost goes down. Pure genius.

    1. Natalie Gritpants Jr Silver badge

      Re: Reduced testing time

      Maybe I'm more paranoid about data storage than Seagate. I would have thought that testing the drive would mean testing that arm1 can read what arm0 wrote and all the other three combinations. You might be able to do write0-read0-read1, the write1-read0-read1 but still it means the test takes twice as long a single arm disk.

      Or is there no ability for one arm to read the other's data? In which case a 30 TB dual arm drive is really two 15 TB conventional disks jammed into one package in a RAID0 format. If that is the case then the only advantage is space and power saving and no speed advantage.

      1. Boothy Silver badge

        Re: Reduced testing time

        It reads like it's the 2nd one you state. i.e. Two sets of platers, each with their own actuators, sharing the same spindle, case and controller.

        Also if it's RAID 0, aka stripe, then you'd be up to doubling the performance, as you can be reading or writing to both sets of platters at the same time. i.e. half the data via 1 actuator, the other half via the other.

        Although I'd assume any performance gain is going to be dependent on the structure of your data?

        1. Anonymous Coward
          Anonymous Coward

          Re: Reduced testing time

          Its not raid 0, its presented to the host as 2 drives.

          This is, 2 smaller drive in 1 case, with 1 sas and power interface, with 1 spindle, but 2 sets of actuators.

      2. gnasher729 Silver badge

        Re: Reduced testing time

        The pictures that I saw were 10 platters, and five read/write heads for the top five platters connected, and five read/write heads for the bottom five platters connected. Instead of all ten heads connected. Like having two hands with five fingers each instead of one hand with ten fingers.

        It's very significant space and power savings compared to a RAID drive, and speed advantage compared to a single disk drive.

  4. A Non e-mouse Silver badge
    1. Flocke Kroes Silver badge

      Re: Conner Chinook

      Chinooks had two heads per surface. A MACH.2 20TB drive is more like 2x ordinary 10TB drives that share an enclosure, motor, controller and power/data connections.

      1. MacroRodent Silver badge

        Re: Conner Chinook

        From the article: "In 1996, Conner Peripherals was acquired by Seagate."

        Maybe the multi-head ideas came from there. Or at least the related patents, so they don't have to worry about some troll coming after them because someone had patented the obvious idea of speeding up drives with multiple heads.

      2. John Brown (no body) Silver badge

        Re: Conner Chinook

        "Chinooks had two heads per surface. "

        I must admit, from the initial headline, this is what I was expecting. But considering the tolerances on modern HDDs, I suspect two heads accessing the same platter for read/write operations might be a bit trickier than the lower density data tracks of the past.

        I wonder if anyone is looking at one head per track? eg a bar across the platter with "heads" stacked across similar to the old drum storage or flatbed scanner technology.

        1. DS999 Silver badge

          Re: Conner Chinook

          When I heard about this a few days ago I assumed the same. When I saw the claim in the Reg article about reducing cost I was thinking "how in the world can having two actuators and sets of heads reduce cost?" It makes sense though if each actuator can access only half the surfaces that you could test in half the time, and presumably that makes up for the cost of having the second actuator.

  5. Dwarf Silver badge

    Marketing missed a trick

    Surely they should have called it the Zaphod drive, since he had two heads as well

    1. ShadowSystems Silver badge

      Re: Marketing missed a trick

      And the next version would be the Monty Python triple-headed giant that argues with itself so long the files run away? =-)p

      I just want a 30Tb HDD of my own so I can move all my Youtube Hentai porn off my main storeage array...


      I, uhhhh, I mean move all my copies of *nix ISO's to better places! Yeah, that's what I meant. Absolutely no porn at all, nope a nope a nope.

      *Wanders away whistling innocently*

      1. Alan Brown Silver badge

        Re: Marketing missed a trick

        > I just want a 30Tb HDD of my own

        Samsung can already sell you a 2.5" easily concealable drive for the purpose

    2. steelpillow Silver badge

      Re: Marketing missed a trick

      That would require the resilience to keep walking when one of your heads is confiscated.

  6. Anonymous South African Coward Silver badge

    We demand a video showing the hard drive in operation! :)

  7. Wolfclaw

    WOW talking up an idea that is logical and should have been done years ago, DOH !

  8. Mike 16 Silver badge

    Random IOPS

    If I am reading the article correctly (and it appears from the existing comments that I am not the only one noticing this), the two head assemblies serve distinct areas (platter sets?) of the drive. So Random IOPS are only boosted to the extent they are evenly distributed between the two "logical" (virtual? semi-conjoined?) drives. Enforcing that means they are not exactly "random".

    Compare and contrast to the IBM 350 (RAMAC)

    which could be had with two access mechanisms, each capable of reading/writing any sector on the disk. This option was introduced in 1958, and the last shipments were in 1961 (from article cited, so you don't _have_ to read it).

    Note this was for "one of the last vacuum tube based systems" from IBM.

    The follow on 1405 also (IIRC) had optional dual access mechanisms. Wikipedia

    says "one to three" access arms.

  9. SImon Hobson Silver badge

    Hmm, I'm sure I can recall one manufacturer selling 3 1/2" drives back in the 90s with two sets of heads - because they'd reached the point where moving one set of heads about meant that they couldn't saturate the SCSI bus on random I/O loads.

    Not that I could afford the drives, or a system capable of fully loading it :-(

    Clearly a case of right, it's been long enough now, no one will remember the last time it was done - we can get away with calling this a new idea now !

  10. Sparkus

    dual actuator drives have been long in coming

    but please tell me that Seagate is NOT going to use SMR on these drives........

    1. Richard Boyce

      Re: dual actuator drives have been long in coming

      At worst, you could always buy their NAS drives. Seagate has promised they won't do what WD did.

      1. Sparkus

        Re: dual actuator drives have been long in coming

        Seagate publishes a chart showing which of their drive models do and do not use SMR.

  11. Social Ambulator

    I seem to have missed something…

    …Excuse me for asking, but are drives of this sort still in existence? I thought everything was solid state now.

  12. Anon

    Is it really a new idea?

    This was an obvious idea since hard disk drives were created. Why didn't the massive performance improvement of zero track-to-track delay (taking into account rotational latency) for larger files, and better performance anyway, from having two complete sets of heads ever become a thing? Or did it, and it never made it to user-level compoinents?

    1. DS999 Silver badge

      Re: Is it really a new idea?

      Because having two COMPLETE sets of heads doubled the cost of the most expensive component, and increased power draw. It was tried, but never succeeded.

      It probably only became feasible now due to the increasingly long time it takes to read and write a full drive's worth of data, due to the continual increase in the number of tracks per platter. That meant testing times got longer and longer, and it sounds like Seagate decided that with a modification that each actuator carries only half the heads (keeping the cost of heads per drive constant) the cost of the extra actuator was less than the money saved by halving testing time. i.e. they didn't do it for performance reasons, they did it for cost reasons.

  13. DS999 Silver badge

    So why not MACH.4?

    The drive has four corners, so there should be room for four sets of actuators. Maybe the "decreased cost" thing is no longer true as adding one actuator and saving 50% of original testing time isn't the same as adding two more actuators and saving another 25% of the original testing time aren't equivalent. But even if it cost more, another doubling of IOPS and throughput would probably be worth it at a modest premium.

    Such a large percentage of HDD market is used in RAID parity configurations these days, where rebuild times become longer and longer as capacity increases, that rebuilding 4x faster would be necessary down the road when we get to the promised 50 to 100 TB drives just to keep rebuild time relatively constant. Single parity is already untenable in most situations due to the length of rebuilds, even double parity is problematic in some situations.

    I would imagine you probably get more than double the IOPS from MACH.2, because with each actuator having only half the heads, they are lighter which reduces seek time.

    1. 7teven 4ect

      Re: So why not MACH.4?

      Like, why not run, then, walk?

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