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Next Wave Of Hard Drive Tech: Perpendicular Recording
angrytuna writes "New serial technologies are set to replace standard SCSI and ATA (Advanced Technology Attachment) interfaces over the next two years, even as hard-disk drive manufacturers prepare for an entirely new form of bit storage. Perpendicular recording will replace longitudinal recording in storage devices, placing bits on end instead of lying them parallel on the disc surface, thus dramatically increasing the possible storage density."
that there is such a crackdown on file-sharing. If they take that away from us, then whats the point of having that much space?
I wonder which side of the debate the hard-disk manufacturers are on?
If my drive bit is standing up, it must be hard. Ergo, hard drive.
C|N>K
I am less concerned about the amount of stuff I can put on a hard-drive, and more concerned that the next time I boot up my computer, that stuff will still be there, as harddrives get more and more high-tech, the reliability seems to be taking a big nosedive, how will this effect the reliability of future drives?
In the days of 250GB hard drives, who cares? All I'm concerned about is the speed of drives. Lets improve that for once...
Does anyone have a link to a description of this that's more detailed than "stacking bits on end"?
Are they using platters with trenches and storing information on the sidewalls?
Are they using some means of reading and writing at many depths within the platter without disturbing other layers?
The article says the technology has been under investigation for 20 years, so presumably there's a forest of technical literature on it.
HDD manufacturers said they expect to start replacing 3.5in. disk drives with smaller 2.5in. devices in enterprise products sometime within the next year.
Why would they want to do this? Has it something to do with vibrations (or even shattering a disk) due to the extreme rpm's that these drives are running?I don't know much about this stuff, so could someone please enlighten me?
The best weapon of a dictatorship is secrecy, but the best weapon of a democracy should be the weapon of openness.
This conversation with Jim Gray, head of Microsoft's Bay Area Research Center, has grim, eye-opening comments on the growing gap between storage densities and access speeds/bandwidth. Currently the most effective way to send a multi-terabyte disk array is by UPS -- turns out a UPS truck has a "bandwidth" equivalent to about 7 megabytes/second. And the problem of practical access speeds is only going to get worse. At current and near-future access speeds, searching a 20-terabyte disk might take a year.
Storage density is one thing, but storage speed is another. With 200 GB hard drives readily available, and relatively cheap, the main thing I'm itching for is increased access and transfer speeds. Not just the controller speed as most hard drives still only maintain a constant transfer speed of 33Mbps. Theoretically, a denser drive at the same rotational speed will transfer data faster than a less dense drive, but will we see a dramatic improvement in sustained transfer speeds? While this transfer speed is acceptable while watching a DivX movie, it's really a pain while ripping a DivX movie. (A movie that I shot in my backyard, and authored, and own the rights to, and am ripping for the pure exitement as I would never violate a copyright.)
Could someone explain (/point me to a website) as to what this paragraph means?
"We always have concerns about new connectors and backplane designs but those problems are minimized in a serial environment where the wiring is point-to-point,"
"Connecting devices fast is a lot easier when there's only two of them."
If they stand the 1's up, sure you can fit more because they're skinny. But 0's? They're wide...I don't see a significant amount of savings there...
So, does this mean that instead of looking like this:
0
1
All of my bits will instead look like this?:
_
-
I suppose you can squeeze a lot more of them together that way, but is that really much of an innovation?
Now, if they had figured out a way to fold the suckers, I'd be impressed.
More relevant than this technology that is still many years away, I find much more interesting the part about the desktop industry moving to 2.5" drives. So in the next year or so we'll be able to buy very high density, fast drives that can fit in a pocket and already have serial interfaces! All we need are sata jacks on the front panel and the world moves one giant leap closer to true "plug-n-play" goodness. Mail order sneakernets just got even cheaper!
I have seen a few posts from folks not quite understanding how the "bits-on-end" approach works. Some were speculating that it might be holographic, multiple layers, or 3D and such. It is not at all that complicated as they are making it out to be. I heard it best described from Alan Shugart who started the company called Seagate. On an episode from "The Computer Chronicles" back in 1984 he described it as standing the magnetic particles on end to fit more in a given area, which is similar to how a cord of wood could fit into a given smaller area by standing them up on end instead of laying flat. So it really is simpler than you might imagine. Of course the implementation is anything but simple. This is especially evident by the fact that this idea was known as a way to increase storage density back in 1984, when even 200 million bits per square inch was not in a consumer product yet. It was merely in labs with thin film head technology poised to become the next big thing in a short time from that year.g er.php.
By the way, you can see old episodes of "The Computer Chronicles" at the Prelinger Archives collection.
http://www.archive.org/movies/prelin
I believe Slashdot had a story about that a while ago. Good stuff! Great info can be had through those old episodes about computer history.
>>>>>> Chewie, take the professor in the back and plug him into the hyperdrive.
One of the first Sun machines I used was a 3/160 with an external gigabyte disk array. The array was a washing machine size enclosure with a pair of 800 MB SMD disks with 8" platters. In 1994 this was a huge disk, in more ways than one!
Interestingly, my little 486 with its 340 MB drive were far faster than the old Sun, and even competitive with the newer SparcStations. 7200 RPM baraccudas in modified enclosures (extra fans and breathing holes made the difference between life and death) were even faster when they arrived.
After working exclucively with laptops for the past two years, I can see a clear parallel between the old 2.5" -> 2.5" transition and the 8" -> 5.25" -> 3.5" transitions in the past. Sure I keep a pair of 120 GB 3.5" disks in firewire enclosures around, but the 60 GB disk in my powerbook and the 30 GB disk in my Dell i8000 are more than adequate for daily use. My ipod even has 30GB, which is enough for my favorite music, the Warthog Jump video and a few other fun things.
With emphasis on blade and 1-U servers, as well as cardcage oriented telecom gear, I can see a lot of value for 2.5" disks in the telecom and server markets.
Interesting? This clueless and sadly-late attepmpt at a FP is misleading everyone that reads it!. And you mods are to blame -- that's right: YOU!
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Grrr, RTFA: there is nothing "3D" about it. It's still a 2-dimensional array of bits on a platter. The density increase comes from standing the little areas of magnetic media on end, instead of laying down. So, a top view of the old scheme would look like:
||||||||
||||||||
The new scheme, from the top:
In this case 2x density, as the lower one has twice as many dots in the same area as the dashes of the upper. (That is, each dot or dash represents the area of the physical medium used to store one bit by changing its magentic orientation). Get it? No 3-d. No holograms. Just 2-4x density increase by changing the orientation of the bits from parallel to perpendicular (relative to the disk platter surface).
everything in moderation
An article which simply jumps into a description of an esoteric subject can seem awkward and be difficult to understand, so journalists have long been taught strategies for lessening that initial impact. Many of these conventions don't play as well in the internet environment because a linking page has already told the reader what the article will really be about. This makes the lead seem like irrelevant wandering.
See, there's a limit to how many bits you can store on a disk. I see. Because the area of the disk is limited I see. But you don't want a limit, you want more space. I want more space. But you can't have more space, because all of the bits are square they're square. and there's only so many square inches of surface. Only so much. Yes. Look at this disk. Radius 3.25" 3.25 It's a circle. It's round. Pie-R-square Pie-R-square So the area's limited. I see.
And the bits, they're almost square, because that's the way the manufacturers' engineers like them. They like squares? Yes. I see. Well, really they're not square, they're almost square. And how's that? Well, they're square sections of a round arc. Not square? But almost square. Almost square. I see.
So what do we do? I don't know. Well, we get a better packing fraction. Better packing fraction? Yes. That's the key. A better packing fraction. I see. And your data is round. Data is round Because the magnetic field is round. I see. And a square doesn't approximate a circle very well, does it? No. What does it better? A circle? Well, yes, but you can't do it with a circle, because circles bump each other. They bump each other? Yes, and they leave empty space between them. And we want a better packing fraction? Yes. So what do we take a cue from? I don't know. I know you don't know, but I'll tell you. We take a cue from the bee. The bee? The honeybee. He uses hexagons. Aaah. Hexagons. Yes, hexagons. They're all the future. The future? The future. The future. Yes, the future. Hexagons. Yes. That's where the money is. You're a nut.
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
If you have no idea what the difference between Longitudinal Recording and Perpendicular Recording might be, and the phrase "stands the bits on end" meant absolutely nothing to you because its an utterly ridiculous way to explain it, here's the lodown. Longitudinal recording is what we use today in everything from cassette tape to hard disks. It works by magnetising tiny sections of the recording medium. You can imagine the magnetised sections as tiny bar magnets laid end-to-end. The read head detects transitions in the direction of the magnetic field.
.
<- -> <-- -> <- -->
In the above diagram we're looking down at one track on the surface of a platter. Perpendicular recording works differently. The "magnets" or bits are arranged so that the field they emit is perpendicular to the medium, like this:
x . x . x . x
In the above diagram we're looking down at one track on the surface of a platter 'x' represents a field pointing away from us, '.' is one pointing towards us. This is what it looks like in cross-section (looking in from the edge of the platter):
^ | ^ | ^ | ^ | ^
| v | v | v | v |
In perpendicular recording the read head detects the actual direction of the fields emitted by these bits/magnets, rather than transitions in the field. Perpendicular recording is advantageous because it allows one to use a much smaller surface area on the medium for one bit. Imagine if you laid a line of bricks end-to-end on the ground, you could make the line shorter but taller if you stood each brick on end (so they're laid flat-to-flat), but you've not had to make the bricks any smaller in order to acheive this change in the length of your line.
Most of the above is hopefully right. Anyway it's a better explanation than that site gave.
Both schemes store the bit to some depth physically. You can't have an infinitely thin bit. Both schemes also still use a 2-D grid of bits. (Well, polar grid, since it's a spinning disc.)
A truly 3-D organization of bits within a single platter face would be something like those multi-layer DVDs, where within the same grid position you can access multiple bits by changing some aspect of the reading mechanism. (In the case of the DVDs, it's achieved by focusing the lense differently so only the desired layer is in-focus.)
--JoeProgram Intellivision!
Don't make fun of my floppy. I know it's small, but I use it alot. :(
Life is not for the lazy.
ASCII art is great for porn but for technical stuff I prefer real images. This image cleared things up for me.
Well, in my experience, engineers only like to brag about a new technique if it gives a 10x improvement. (Or more.) If you read the article, you would have noticed some numbers:
:)
:)
The "brick wall" in magnetic recording is called the superparamagnetic effect. This is the point at which the recorded data starts to get lost in the thermal noise of the media. (As you approach the superparamagnetic, it becomes statistically likely for recorded bits to sporadically flip states resulting in data corruption.)
For longitudinal recording technology, it is estimated that superparamagnetic will start to become a problem around 100Gbits/square inch recording density. (Current hard drive technology is around 50Gbits/square inch - so they are getting close to the wall.)
Perpendicular recording technology is estimate to scale up to around 1Tbit/square inch.
Now, what did I say about engineers liking to brag about 10x improvements? Well, 1Tbit is about 10x improvement over 100Gbit. How about that!
What this means to you: if current hard drives store about 120GB using a recording density of about 50Gbit/square inch, then we can expect perpendicular recording to eventually deliver drives that store about 2.4TB extrapolating up to a 1Tbit/square inch. Even if this technology only works half as good, at least we will eventually have hard drives that store 1TB!
On top of that, the article say they are moving away from 3.5" drives toward 2.5" even for "enterprise" applications. Now, if we get 1TB drives in 2.5" form factor that's going to result in some killer MP3^^err...uncompressed 24bit, 192kHz iPods
Although the solution proposed in the article would increase storage capacity by, say, a factor 2 or 4, it still is a temporary solution that does not solve the fundamental problem at hand.
The fundamental problem is the superparamagnetic limit: if you make a magnetic domain (a bit) smaller than a certain size, it becomes thermodynamically unstable. In English, this means that very small bits loose their value after a while. It also means that for the time being, we'll have to use tricks to pack the bits closer together while keeping them large enough to be stable.
It should be noted that perpendicular recording is not the only effort to achieve higher recording densities in the looming shadow of the superparamagnetic limit. Indeed, harddrive manufacturers have seen this problem coming for a number of years now, and have had meeting to discuss possible solutions.
On a brighter note, there seems to be progress in circumventing the superparamagnetic limit: very recent research show promising results for the future.
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The rotational speed of the drive is directly related to the access time. If the data you want is on the other side of the platter, you must wait for it to rotate 180 degrees before you can start reading, regardless of whether the disc is 1/2" in diameter or 2" diameter, whether there are 1GB per square inch or 10GB per square inch.
When the head gets lined up with the track and ready to read, the data it's waiting for can be anywhere between 0 degrees and 360 degrees away. If you average out all those possibilities, you can expect the data to be about 180 degrees away.
Now, a 15000 rpm drive rotates 180 degrees 30000 times per minute. Conversely, it takes 2ms to rotate 180 degrees. If you consider that a typical 15k rpm drive has an average seek time of 3.3ms and we know that 2ms are spent waiting for the disk to spin, than 1.3ms must be spent moving the head. This proves to me that rotational speed is more important to access time than data density.
I'm no hard drive engineer, but I would bet that an increase in density would mean a decrease for rotational speed since a read head probably has a limited bandwidth. (This is probably why the faster-spinning drives typically hold less data.) If you halve the time moving the head while doubling the time waiting for spinning data, you will see an overall increase in seek time.
My conclusion is that greater density and less rpms would hurt access time which is the most important performance factor. However, like the "MHz myth", I'm sure marketing will focus on bandwidth benchmarks for performance instead of real-life application performance.