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The End Of The Road For Magnetic Hard Drives?
Phase Shifter wrote to us about the limits of conventional hard drives, which Scientific American is discussing. The article talks about the history of hard drives, and why sometime soon, due to the limitations of the superparamagnetic effect, we will need to find a new storage type. It's a cool background read on hard drives and what goes into them.
A Brief History of Hard Drives
(a la Book-A-Minute).
Scientists: OH NO! Hard drives can't get any better!
Engineers: Wait! Your science is WRONG! (Writes some new equations).
Computer industry: You have SAVED us!
Geeks: YAY!
Xerox is sponsoring a research of 3D storage devices that can manage tens of thousands of gigabits in a volume of sugar cube at the University of Toronto
You can't handle the truth.
Hard drive technology has progressed at least as fast as other computer technologies. Let's compare the present day to the day of the original IBM PC XT, some 17 years ago.
Processor, 4.77 MHz -> 600 MHz: 126 times
(let's say 1000 times, because the P III does a lot more with each MHz than the 8088)
RAM, 64 KB -> 64 MB: 1024 times
Modems, 9600 baud -> 56K: 6 times
(even 1.5M for cable modem is only 156 times)
Hard disk drives, 10 MB -> 20 GB: 2000 times
Hmmmm, seems like the much-poo-poo'ed electro-mechanical technology has easily kept pace with the straight electronic technologies, including the breathtaking advances in chip density.
Now, when it looks like CPU speed and RAM density really ARE about to reach a plateau for a while, or at least lower its slope of advance, hard disk technology is poised to really rocket ahead. Look at the news from IBM research, foretelling VAST advances in the fairly near future.
I don't have a link to this info handy, but my recollection is that bubble memory was _way_ too slow - and hard drives just kept getting better ...
... but at least some of that will be due to the massive research that has gone into making the current technology work well.
It seems to be a bit of a trend in this industry that whatever works early on gets a lot of resources put into incrementally improving it and making it cheap, such that competing technologies have to be _hugely_ better to have any chance of taking over.
That is (IMO) partly why:
- we still use hard drives,
- CPU's still use CMOS rather than one of the faster switching methods,
- the x86 architecture is still dominant,
- the UNIX model is the base of nearly all operating systems.
There may be potentially 'better' technologies than these out there, but there has been so much engineering and optimisation gone into these technologies that it is really hard for anything to compete.
The case of the Exponential PowerPC is an example of that - it used ECL rather than CMOS to get substantially higher clock speeds, but before it had really got up to speed, the incremental improvements in CMOS had passed made it look less attractive, and Exponential was dead.
I expect someone to reply to this and say how much better CMOS (or whatever) is better than anything else
Since everyone will be replacing their hard drive with rolls of scotch tape, I'll corner the market!
Fight Spammers!
Then, one day, someone realised that - hey! If you throw away the assumption that baud == bps, you can actually drive up speeds to 56Kb/s!
Then, as modems went up in speed, the same engineers moaned and groaned. The 56Kb/s limit was near, and without a total rewiring of the phone network, an act of Congress in the US (an act of God elsewhere in the world), and more money than anyone had, the 56K barrier would never be breached! Calamity!
Then, one day, another bright spark realised that if you had modems at the junctions, you could shove REALLY high-speeds down the wires without either Congress -or- God having to do anything. (Much to the relief of both.)
The Doomsday Crowd, defeated once more, lurked on the fringes. Until, one day, redemption! Hard Disks can't pass a certain density!
This, of course, is as bogus as all the other claims. If it's possible to read the past ten writes on a given sector, then you can you can increase the density of the disk by AT LEAST an order of magnitude. You just have to remember to read/write all ten layers at one time, and you're fine.
Then, of course, there's no rule which says you have to use 2-state logic. It's easy, but it's not mandatory. Magnetic fields can have any orientation and any strength. So long as the maximum strength isn't so high that you get bleeding, you're fine. Recognise 256 possible states (using any combination you like of orientation and strength), and you've "encoded" a single byte into a bit - a x8 gain in disk capacity.
Combine the two, and you've increased the capacity by over 80 times! This can be increased still further, by increasing your ability to scan over-written layers, and by increasing your ability to distinguish magnitudes and orientations. You have two degrees of freedom for rotating the magnetic field, which means that by doubling the ability to distinguish, you quadrouple the number of possibilities available.
The scientists may be correct about the density, but the density is NOT the only variable open to hard drive manufacturers. In the future, it may become one of the least significant, as others are explored.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Size is the only dead end in site for hard drives.
- Speed. The average hard drive is spinning at 7200 RPM nowadays. At this speed, there is an average latency of 4.6ms just to spin the track under the head. You can't do much about this except spin the disk faster. At 10000 and 15000 (thanks Seagate), you still have 3ms and 2ms, respectively. This is on top of any time needed to move the head itself. With most access times <8ms in the low end and <5ms in the high end, this ceiling isn't too far off. Sure you can spin the disk faster, but this gets expensive (money, energy, and heat).
- Size. I think the article addresses this quite nicely. If we hit the ceiling here, we can increase the surface area. But this again gets expensive in all ways and precludes a 100 GB laptop drive in a 1.5 in width and 1 watt power consumption. You know you want it.
- Reliability. To me, this is the biggest problem. Hard drives are the most relied upon moving part in a computer and yet are the first thing to go in most systems (followed closely by the power supply, who's death is usually hastened by a power hungry hard drive spinning up and down). RAID (or similar) can tackle this, but is expensive in all ways and requires the user's attention.
Finally, I won't argue that hard drives will meet their doom in 5 years, hell we don't even have a suitable replacement yet (only stuff in research). I just figure they will be a story that I will tell to my grand children.Mmm hmm. And do you think anyone would have gotten around to that realization had someone not observed that the "baud == bps" approach would not work forever?
Right, but would anyone have bothered to do this had someone not pointed out that you couldn't get higher speeds using the conventional approach?
The moral of the story is that there is value to pointing out the limitations of current technology because that is what allows us to avoid wasting effort by developing new technologies to replace existing technologies that don't need replacing. Conversely, it helps to anticipate problems in existing technology before they start to limit progress, so that new technologies will be ready by the time those limits are reached. This is not "doomsaying", it is simply having a good understanding of current technology. You have to have a thorough understanding of existing technologies, including their limitations, before you can hope to improve on them.
-rpl
Wow, it really is Scientific American. Down with metric!
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