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Data Storage Hardware

Phase Change Memory Points To Future of Storage 70

Posted by Soulskill
from the how-many-gigaquads-does-it-hold dept.
An anonymous reader writes "A UC San Diego team is about to demonstrate a solid state storage device that it says provides performance thousands of times faster than a conventional hard drive and up to seven times faster than current state-of-the-art solid-state drives. The drive uses first-of-its-kind phase-change memory, which stores data in the crystal structure of a metal alloy called a chalcogenide. To store data, the PCM chips switch the alloy between a crystalline and amorphous state based on the application of heat through an electrical current. To read the data, the chips use a smaller current to determine which state the chalcogenide is in."
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Phase Change Memory Points To Future of Storage

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  • My very first reaction was to think of Asimov's Foundation trilogy and the fact the the Galactic Library was stored as nicked quanta in a paperweight on the Librarian's desk. The Barbarians allowed him to take his personal belongings with him before they destroyed the Library Planet.
  • No longer will I need a huge magnet, now I just need a hair dryer!

    But Seriously, wouldn't external heat sources pose a problem for such a technology? I don't want my drive erased next time my electricity goes out during the summer.
    • by bmo (77928)

      >just need a hair dryer!

      Honey?
        yeah?
      Can I borrow your EZ Bake Oven?
        But daddy, the police took it last time...

      --
      BMO

    • If you have issues with your house going 600C without AC you may have other issues. Not to mention high heats have just as detrimental effects on magnets.

  • To store data, the PCM chips switch the alloy between a crystalline and amorphous state based on the application of heat through an electrical current.

    That seems like probably not a very good idea, and I'm sure it will end up being one of the major hurdles to this technology really getting off the ground. What happens when the memory is heavily used (leading to buildups of heat in the memory that could cause unintentional bit changes)? Obviously the heat used to flip the bits must be dissipated very, very quickly, and that's a pretty challenging problem in its own right. Also, what happens to system temps when you use this memory? Many systems are already difficult to keep cooled, and adding another source of heat could be a particularly bad idea. Heck, what if the increase in system temps leads to memory faults? After looking over the Wiki, the last question seems unlikely to be a problem, but heating something to >600C seems like it could make it very hard to use this tech in heavy use situations.

    • It sounds a lot like magneto optical drives, like MiniDisc. It probably takes very high heat (good for room temp stability, i doubt your hairdryer would do it) in a *very* small place for a *very* short time. Probably, the stability is very good or they uh, wouldn't be excited about it. I don't think the dynamics of the room would be affected any more (probably less) then a typical HD. Check out: http://en.wikipedia.org/wiki/Magneto-optical_drive [wikipedia.org] it's fascinating
    • I saw this same principle being used on CDs: in the crystalline state, it reflects much more light than in the amorphous. IIRC, to change into crystalline, it required more than 130 C, but take it with a grain of salt. What I'm sure is that it was a lot hotter than 50 C, otherwise I would've thought the same as you.

    • As someone who has done research in memory wear leveling, I can assure you that these technologies have a place. There are significant design trade-offs that must be considered for any application. Power, area, speed/latency, and maximum amount of write-erase cycles all come into play. One of the head researchers in emerging memory technologies at Penn State has an interesting presentation here on the roles of these memory technologies (yes, I realized it is hosted at Oregon State, and he is from PSU, oh
    • by jbengt (874751)

      Obviously the heat used to flip the bits must be dissipated very, very quickly, and that's a pretty challenging problem in its own right

      Fortunately, the smaller the memory element, the less heat it takes to raise its' temperature. And fortunately, or unfortunately, depending on your point of view, the smaller the memory element, the faster and easier heat dissipates from it. I'm sure that one of their criteria is to select materials that do not spontaneously switch states at the temperatures typically fo

    • by sjames (1099)

      It's not as much heat as you might think it is, it's just very concentrated. Same reason you can use a laser to heat something hotter than the surface of the sun without even warming the room noticeably.

  • skimmed some papers on PCM on the web, looks like their goals are to get the memory to 100 million writes and 10 years retention of data; very similar issues to flash, it seems
    • Looks like you did just skim. PCRAM has two fundamental differences from flash:

      It's bit-erasable. You can write a single word to PCRAM, without having to do the read-erase-rewrite cycle that Flash requires over a large cell. This means that you can just map a PCRAM device straight into RAM and use it as (slowish) memory. This is great for things like applications - the entire binary can be run from the mass storage device, it doesn't need copying into memory (execute in place). For a mobile device,

      • by sjames (1099)

        It would also get rid of much of the weirdness of SSDs. Most of that is because of the largish erase regions compared to block size for a filesystem and the time it takes to erase a sector.

  • by roman_mir (125474) on Friday June 03, 2011 @11:07AM (#36331344) Homepage Journal

    So, what's up with the name of the system, "moneta", is it what I think it is (a Russian word for 'coin'), or is there something else at play here? I am a bit confused, because in the article, (which I am sorry to admit I read), it mentioned a bunch of names, but none that were Russian sounding.

    • by Anonymous Coward

      Check this out on Wikipedia:
      http://en.wikipedia.org/wiki/Moneta

      Goddess of memory...

  • I actually skimmed the article and I didn't see any mention of data density. Anyone know how it compares?

  • Phase change memory tech is not new as most readers here will know. Nearly all the major semiconductor companies have worked on prototype versions of this tech. If companies like Samsung and Intel haven't succeeded in mass producing it yet, as a consumer I'd be more interested in knowing what sets this particular device apart from all the others that will make it more likely to reach the market for the masses. Cheaper to produce? Scales more easily? More energy efficient? More stable?
  • Is what is the number of cycles before a given bit can no longer be changed. Will this outlast the current SSD write cycle limitations that are getting smaller not longer with the ever shrinking die size thus resulting in having to have 2x or 4x the actual advertised RAM installed to meet ever increasing MTBF rates..
  • If it works as described with the PCB generating heat to change the substance from a crystal to a liquid, once that heat is removed via loss of power, all would change back to a crystal, and you would lose all your data. This may be fine for RAM, but not for storage.
    • by Tapewolf (1639955)

      If it works as described with the PCB generating heat to change the substance from a crystal to a liquid, once that heat is removed via loss of power, all would change back to a crystal, and you would lose all your data. This may be fine for RAM, but not for storage.

      Actually I think you'll find it's the same material and a similar principle to CD-RW disks. The difference is that in CD-RW they are heating it with a laser, and reading it back optically. In PC memory, they are probably heating it electrically, and they are using a change in resistance rather than a change in reflectivity to read it back.

    • No. Power is needed for the phase change (flipping a bit). PCRAM is non-volatile - it does not require power to retain its state. That's the entire point...
    • by robot256 (1635039)

      It's not switching between solid and liquid. It's switching between crystaline and amorphous solid (stated in the first wikipedia intro, second link in the article). It takes a small amount of heat to make it switch between the two states, and they have different properties that can be measured, but both states are static in the absence of heat. What you described would make no sense at all, since if the PCB knows to provide heat to certain places then it already has external memory.

      Of more interest is

  • A UC San Diego team is about to demonstrate a solid state storage device that it says provides performance thousands of times faster than a conventional hard drive and up to seven times faster than current state-of-the-art solid-state drives.

    I don't know why, but the speed comparisons in the summary amuse me. "This is THOUSANDS of times faster than a conventional hard drive — absolutely phenomenal speed gains, faster than anything else ever seen in the conventional hard drive world , speeds which will blow your mind straight out of your skull with how much blindingly faster they are than conventional hard drives, literally THOUSANDS of times faster — and kinda sorta faster than solid-state drives."

    • by dgatwood (11270)

      It reminds me of this:

      Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
      —Douglas Adams

    • by robot256 (1635039)
      Yeah, you're right, that is kind of distracting. That it's sorta faster than solid state drives is nice, but what we really want to know is if it has better power, reliability, or density. Given the recent fuss about SSDs failing with no warning, it would also be relevant to compare the data retention reliability of PCM with magnetic hard drives, but certainly not the speed.
    • Yes, I didn't know solid state drives were already hundreds of times faster than hard disks.
      • by ShakaUVM (157947)

        >>Yes, I didn't know solid state drives were already hundreds of times faster than hard disks.

        Heh, you're right. Consumer grade SSDs aren't hundreds of times faster than a HDD. Maybe one order of magnitude faster at sustained combined read/write (my SSD benched in at only 3x faster than my new HDD), but the real gain is in latency. Maybe that's what they meant by "faster". =)

      • by bobbozzo (622815)

        They are, if you measure in I/O operations per second (IOPS), which is how enterprise-grade storage is often measured.

  • I'm struggling to understand what these researchers have made, exactly. They certainly didn't invent phase-change memory, and the article states that this "Moneta" uses memory modules from Micron Technology. The wikipedia article mentions Samsung started shipping modules last year, ready for use in mobile applications. So clearly PCM has been available for some time. So perhaps Moneta is an actual device available for end users? That would be exciting!

    Swanson hopes to build the second generation of the Mone

    • by daedae (1089329)
      You quoted one part of the article, but you missed the relevant bit.

      "We've found that you can build a much faster storage device, but in order to really make use of it, you have to change the software that manages it as well. Storage systems have evolved over the last 40 years to cater to disks, and disks are very, very slow," said Swanson. "Designing storage systems that can fully leverage technologies like PCM requires rethinking almost every aspect of how a computer system's software manages and accesses storage."

      So you're right, they didn't invent PCM, but they're coming at the problem with the assumption that PCM will become commonplace and then looking at the problems that come after that. All the speed and capacity in the world are only helpful up to a point if your software stack and memory bus are bottlenecks.

      • by daveman_1 (62809)

        I've spent all of two days now reading about PCM, but here's an observation: The lessons learned in making NAND flash work as a high-speed storage medium are applicable here as well. Many of the problems are the same, with the need for wear-leveling and optimization of write performance. The solutions appear to be somewhat different though. Their wear-leveling algorithm does not at all resemble the complexity of a typical FTL and I think that's the point.

        Dealing with the problems of getting this technology

        • by daveman_1 (62809)

          Actually, it's 40 chips for 640MB on a DIMM. The sample they demonstrated was 10GB in total.

  • "switch the alloy between a crystalline and amorphous state"
    Interesting, this is similar how cd/dvd-rw works, where they use a laser to do the state change.
  • OUM/OVM memory for storage applications. The IOPS should be quite nice once done properly.

Never put off till run-time what you can do at compile-time. -- D. Gries

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