How Hard Drives Work

that in a long time. That's true, Well, we haven't done in a long time. So today's episode comes to us as a result of many, many listener males, and so I'm not gonna read them all, but to Kara, Ryan and Justin in particular, and I'm sure there were more, but those were the three who popped up immediately. Um, this podcast is for you. All of you guys want

to know how hard drives or hard disks work. So we're gonna talk a bit about hard drives, and not just not just the old fashioned hard drives, but the new fangled solid state devices as well, and throwing some some other storage media. I think oh I got, I got a little bit on some others, notepads, and yes, exactly stone tablets, stone tablets. So let's let's talk about let's talk about the anatomy of a hard drive. Okay, I was going to start out with a little history.

Oh that is even better, begin with your history, professor Palette. Um, I'll tell you a little bit of a story. My first computer wasn't Amigo one thousand, which I got in the mid nineties, and it had no hard drive whatsoever.

My Apple to eat also had no hard drive. So you might think that hard drives, which are now you know, ubiquitous there in almost anything, including you know, uh, tablets and you know, netbooks and things that that are very small, you might think, well, hey, you know these have been around for a very short time. Not the truth. Oh weird. I was just thinking they were amphibious. So anyway, amphibious

what you said? Okay, So no, uh, hard drives actually have been with us since the nineteen fifties, except they were very very large. Um and uh it's apparently up to in diameter and they would hold just a few megabytes, which is very much like the first hard drive I had in my second computer, the Mega three thousand had well actually still has a hard drive that will hold uh, you know, just forty megabytes, which is very small. But but these original discs were called fixed disks, or if

you were an IBM customer, you might know them as winchesters. Um. And basically the reason they're called hard hard disks are hard drives is because this is in contrast to floppy disks, which are you know, made of a magnetic storage medium very much like uh, tape that you might see in a cassette tape or an eight track tape or videotape. Um. But hard drives themselves getting into your into your anatomy

uh lecture on hard disks here. Um. Yeah, they're they're actually not that dissimilar because hard drives are also magnetic media, right, but they are glass or aluminum or some form of harder material. It's not like that filmy, flimsy stuff that you would see in a cassette tape. Right. So that's where the hard drive or hard disk comes from. We're talking about. It's stored on a medium that is uh,

that's that's not this little flimsy material. So that's another thing we should talk about just very quickly, since we're talking about you mentioned floppy disks, which some of our listeners may be thinking hua a floppy disk. Some of our listeners are very young, and I have not been around since floppy disks kind of died. But I like to think of the tech stuff audience as being you know, fairly technology technologically savvy. You know, even our younger listeners

probably know what a floppy disk. Actually, some of the very younger listeners are probably more savvy than we are. So the reason why we call them floppy disks is because the magnetic medium on pond which the data is stored is is flexible. Um. The disc itself may or may not be semi flexible. So the old five and a quarter inch discs, for example, they had a very uh thin protective coating, plastic coating, uh, and you could they were flexible. You weren't supposed to bend them because

it would screw it up, but you could. Yeah. As as a matter of fact, the hard disc predates the floppy disk because Alan Shugart at IBM in ninety seven, uh, you know, came up with an eight inch floppy disk. UM and basically it gradually moved to a smaller disc five and a quarter inches UM, and that debut in

in August. Um. Problem with that particular model was that it had a part of the media was exposed, so you could you could you know, poke it with your finger or you know, a needle, or your cat could throw up on it. Uh. And that's a problem because all of those things happened to me in the same day. That's bad day. Well, poking it with your finger is not such a problem necessarily as the other two. But yeah,

that's the thing. If you crease it or something happens to damage that material, then it makes it very difficult to read. And when they came out with a three and a half inch floppy disk, which is in some use still in Japan, just stopped supporting it. Yeah, like this year, there's some of the supply classet here. Yeah, there's nothing I know of in the office that can run one. No. No, I've seen a couple of older machines with it on there. Oh my gosh, they have

dust on them. I pity those people to use those machines, but to but no, the thing is, when when those came out, they put a little metal slide, said that the computer when you would insert it, it would the computer would move the slide over and be able to read and write information to that floppy disk. And they also had a harder plastic coating so that you wouldn't

fold a three and a half inch disk. Yeah, and uh, since we're into the alternative media thing, I will I will say, you know, as as time went on, uh, and other formats came out. I Omega's zip drive and jazz drive both removable storage media like the floppy disk, just at a higher density you can hold uh, you know, a gigabyte or two on some of the heavier uh discs.

But they're essentially the same thing, you know, removable media. Now, I remember, you know a couple other storage media that were like that, that were that came in a case like that, But we're optical discs. But those really fell out of favor, I think with the advent of broadband connections and really large hard drives. So getting back to the whole hard drive issue and uh and the fact

that we're talking about these other forms of storage. As we were mentioning they were all magnetic forms of storage, yes, just like cassettes. In fact, some of the early computers used cassettes rather than discs. But and and that does also mean that that would also be why you did not want to have your storage medium next to any kind of magnet, because it would could screw up your

your your data. I mean, it would erase essentially your data because it would everything would align to the magnetic field of the magnet and you would no longer have that storage. Well, I mean that's that's part of erasing the information. Magnetizing. So magnets plus computers equals bad. Right, So you're so in all these cases, the information is stored through a magnetic medium. So you've got you've got the disc, and within hard disc you have we call

them platters. That the discs are actually platters, and there may there's usually multiple platters per hard drive. It's not just one disk sitting inside a little metal box. If you were to ever look at a hard drive, it does tend to look like a little metal box. Usually there are several platters within that. And so think of the platters. It's kind of like a uh, I was gonna say, a record player, but what who am I kidding? Smoke gets in your eyes? A record kids? No, please,

those the kids. I'm saying, the kids are not gonna know if I say a record player, Um, think of a serious player that can hold several CDs. They still make CDs, right, I haven't listened to one in ages. Okay, okay, okay. Another thing to mention. If you want to take a part of hard drive to look at this, do it with a drive that you are no longer ever going to use for anything. Yea, because it'll ruin it. Because

it will ruin it. But if you if you take a part a hard drive that is busted and will no longer be used for anything, you will see that there are are silver platters in there. Uh. In some cases there are multiple pladders, right, Like that's what I was mentioning there, yeah, yeah, And and on each deck there's gonna be a little arm that can that will have the device that reads and writes data to those discs. Now, here's the difference between the the platters and say the

cassette medium. Uh, the device that reads and writes data does not actually make contact with the disk. You do

not want that to happen. No, If you hear a clicking noise from your hard drive, that probably means that the arm, the read right arm is actually making contact with the platter, which means it's damaging the hard drive and you should stop using it and get it repaired as soon as you can, because otherwise what's going to happen is it's going to corrupt the data on that disc or it's going to ruin the hard drive and you won't be able to access the information. Right. That's

called a hard drive crash. Yeah, and it's bad head crash actually. Yeah. So so anyway, each one of the platters has of these arms, are sometimes multiple arms more than one, and the arms can move towards the center and towards the edge of the disk, uh dozens of times per second to try and find the data. And

the data is stored. If you were to if you were to look at a platter and you were to be able to see the way data is stored, like you somehow were able to dawn magic glasses and you looked at the platter and like, oh, look at that. You would see that the information is is organized within concentric circles from the edge of the platter all the way into the center. So you just think of those concentric circles. Now, those are tracks, and they would also be organized in wedges, so sort of like a pie

pie and pie. Those wedges are sectors. So data is is always going to be found within a track and a sector, and the computer has to keep track of which sectors and try x have the data ware. You know. That's when it's when your computer is searching for stuff. It's going through all the different sectors and tracks trying to find the correct information. UM and each track within a sector can only hold a certain amount of data.

It's not like you could say, like, well, I've got this two gigabyte file, I want it all to be stored right here on this part of this platter. That's not the way it works, good luck. Yeah, it's going to break that up, uh, that file up into segments and store it on various tracks in various sectors. And it's not even necessarily going to be on the same platter. Yeah it could be. It could be uh across several platters,

depending upon how your data is stored. And UH as this happens, as as you go on filling up a hard drive, UH, these files can get more and more fragmented because there are fewer sectors that have an uninterrupted, you know series that you could store all the information right there, so it's all within the same general area. That's why you want to defrag your hard drive every

now and then. Yeah, the more fragmented your your data get, uh, it makes it that much more difficult for your computer to find all the pieces of a file, and that's going to slow down your computing time. So it's a good idea to keep everything nicely organized so that it speeds you up and makes it a little less frustrating to use your computer on a day to day basis. Yeah, I made this this comparison in a previous podcast, but so you might remember it. But think of your data.

Think of a hard drive as like a h a multi story building, and and your data is stored in boxes. But the boxes are not all in the same room on the same floor. Some of your boxes are on the top floor, some of them are in several rooms in the middle, and then you've got one in the basement. That's kind of the way your hard drive is working. That's the way it might store a file. The bits of the file might be in various sections of the

different platters. Now these platters are spending really, really fast, and the arms are moving very very quickly. So even though it sounds like this is a real mishmash way of doing it, it doesn't take relatively that long for a computer to find the information. Uh. It does take longer as you use the computer. That's what we're talking

about with the whole fragment defragment thing. You may notice as your computer ages that takes longer for you to pull certain kinds of files and programs up and again. Defragging your hard drive can sometimes help fix that a little bit. Yeah, it's not guaranteed to uh to increase your computing speed a thousandfold or anything like that, but it will perk things up a bit. Yeah, it's really Um, what we're talking about here is seek time, Right. It will decrease the amount of time it takes to seek

out that data. It's not gonna make your processor faster, it's just gonna make it easier for the computer to find the information that you want. Um. There's another speed of information transferle that we have to talk about, which is called the data rate. Now, that's the speed at which the hard drive is able to deliver information to your computer's processor. Yep um and those speeds vary depending

upon what kind of hard drive and microprocessor you have. Yeah, the that information is useful when you're looking for a hard drive if you're interested in buying a new drive for your computer. UM. Also the speed at which the platters spin. A lot of people prefer a faster speed. UM. The trouble is that once you get into that in larger drive sizes, you're starting to talk about more money um.

You know. But for things that are you know, speed oriented, like for example, I don't know, gaming, you probably want a faster hard drive or capturing lots and lots of video. If you're capturing let's say you want to capture high definition video you've shot You've shot a film, an HD film, right, and you want to be able to capture that video

onto your computer. You're gonna want a hard drive that spends very quickly, that has a very big capacity because HD footage takes up a huge amount of data space, and you want to be able to transfer the information as quickly as possible. So uh to to just to speed up the whole capturing UM sequence because that takes a really long time depending on the speed of your computer and the connection you're using, like if you were using FireWire, that's that's pretty fast. If you're using USB

two point oh, it's not as fast. It depends on the FireWire, that's true. I'm talking about like I'm thinking of like the most recent USB three, assuming that that ever actually gets to us in a real widespread way, should put USB right back up there with FireWire. Um, someone's going to think about that. Well, the thing is they keep one upping each other. Is kind of an also ran at this point. I mean, I mean, Apple still really supports it, but that's about it, not even

as much as they used to. Yeah, but to the most recent IMAX, that's a totally different subject. I should't even get into it. To the best of my knowledge, the more recent machines do actually that. That's that's relevant though, because if you're talking about hooking up another drive to your computer, like an external drive, you're gonna this is

again something to consider. You're gonna want a nice fast data rate, and you're gonna see on professional computers, top of the line PCs and MAX both are going to have you know, you're you'll have more options like the faster FireWire and the faster USB connections, you know versus you know, something you might see on your consumer level or you know, for example, a netbook or something you're probably not it's not going to be because they're not

designed for you know, high end applications computing on the go. Um So I mean it is it? Yeah, it is relevant. But yeah, as far as I know, the Apple still includes the higher higher speed one port I think on the the the iMac and probably a couple on the power Max. But um, anyway, that's what they call them now, the Mac pros. There we go. Anyway, someone wanted inbout that I wouldn't know I've got an anti Mac bias. Yes, yes,

we've been told. Um so, actually, uh, it might be a good time to talk about some of the drawbacks of hard drives because you know, over time they've become smaller, they've become more efficient. They there, they can be running faster speeds. Um you say smaller, you mean smaller physically so you can run. Well, yes, they can't hold more data. Yeah, but I just want to make sure we clarified smaller. But well, let's take another Apple product into a two perspective.

I have a four G black and white iPod which has a hard drive in it and you can hear it. When you play a song, it spins up and starts accessing the information on there, so they can tell me what tracks are available, and I can I can listen to a song. But Apple has moved away from physical hard drives because of their limitations, like, for example, if you drop one on the ground and it is still spinning, it will likely start to click because it is a

very easy way to cause a head crash. Um, you know, and they're they're not the most durable things in the world. Yeah, they're not necessarily the kind of device you would want to use if you were like, for example, the iPods a good a good choice. Let's say you want to do lots of exercise and stuff. Um, well, if you've got a device that has moving parts in it, then the jitter that it suffers as you run up and down your street or whatever. Um or being chased by vagabonds,

as is often the case with me. Um, I have a I live in a vagabond heavy part of town. I moved from thug Central to Vagabond Bill and it's actually been an improvement in my lifestyle. But that's neither here nor there, Jonathan. Yeah, you know, I do live right across the street from train tracks, so that's true. I'm hoping is listening to this Hobo love. That's gonna

be the name of my first record album. So at any rate you've got this, If you have moving parts and the device as you're jogging around, then clearly then those those moving parts could suffer as a result, and then you could end up shortening the life of your device. To get away from that, you would want to choose some sort of memory format that did not have moving parts. And we'll get into that in just a minute, because you know, we want to dedicate a good amount of

time to solid state. But let's keep talking about the I was afraid I was segway too early. Yeah, well, well I was just gonna say that. We already brought up the magnet thing, right right. But also just the fact that it has moving parts. You know, it has a motor. There's a motor that turns those platters and the arm as well. Um, motors can break down, motors can overheat. Uh, whenever you have the moving parts, there are certain dangers that are going to come with that.

And for most hard drives, those dangers are going to be something that you'd see to prolonged use, right, Like, so older computers are more prone to hardware failure than than computers that are fresh off the line, assuming that you're not buying a limon, yes, and and hard drives

are you know, I'm sure a computer engineer will tell you. Um, someone had told me once that hard drive often fails either very early in its life cycle, and we would assume at that point that it's a lemon or you know, a couple of years down the road, probably a couple is oversimplification here, but I mean it's it's it's not like it's immune from failure, you know, something where you really need to back up your hard drive often because

there is a possibility that something will fail. A mechanical engineer will tell you, as my father, who is a mechanical engineer, often told me, the more moving parts you have, the increased likelihood that something eventually will break, right, because you have more points of failure exactly. So yeah, so that's that's logical. So that kind of explains sort of

the move to the solid state drives. Yes, now, which you know again iPods and zoons and I think just about everybody who has something like that now all use flash memory of some sort and lots of netbooks are using it, not all, but lots of them, as of them, and and you're starting to see it in other things like laptops as well. UM, solid state is has got a few advantages. Uh, it's it doesn't It doesn't store data magnetically. For one thing. It's all about controlling the

flow of electrons, whether gates are opened or closed. Um. Yeah. That's the electronically erasable programmable read only memory aspect of it, or e PROM Yes. I was like what, um, yeah, And it has two different kinds of gates. It's the information is laid out. Think of the information on a flash drive. So we're talking about like the USB drives, or say the chips that you put into a video game controller to store ave games, a camera, yeah, cameras,

the SD cards, things like that. Um, you have a series of transistors and they're laid out on a grid, and you've got uh floating gates and control gates, and these essentially control whether or not electrons passed through that grid, and that's what determines whether the data on that UH in that section of the drive is a one or a zero, right, And because again all information and computers ultimately is stored as a series of ones and zeros, that would be yes, um, and then uh, you've got

so the see I what if I can remember how the rows and columns go. I know that the the row is the word line, and I think the column is the bitline. Is that right? Um, you don't know, I don't know, okay, so um uh yeah, anyway, see if I have that in my home. It's been a long time since I've actually written about solid state drives, and unfortunately I've been concentrating on other things. But in any of the floating gates, link to the row. The row is the wordline. Just do the control gate. Oh

got you? Got you okay, so uh again controlling the flow of electrons for for bits. Now, the nice thing about solid state electronics is that they can be even smaller than the smallest um physical hard drives, so you don't have to have a motor, so that takes up less space right there. Um, they're very very portable, uh, and they can hold a surprisingly large amount of information.

And you know, I remember back when you would get a USB drive and it might or a little thumb drive, a little flash drive and it would be maybe a Meg's And now you know it's no big deal. Like if when I go to conferences, a lot of these companies will put their press material onto a USB drive as opposed to giving you a six pounds of of paper. Right. And in these cases I get for gigabyte or larger USB drives on occasion. Most are around two. But you know they get bigger than that easily. Um, so it's

actually really really impressive. And they don't since they don't have the moving parts, so you don't have the same risk of failure as you do with a a physical hard drive like the platter hard drive. Um, they're both physical. I don't know why I used that word, so please don't write in I know they're both physical. Uh mechanical, I guess I should say, because it has a quitter function.

The downside is that solid state electronics tend to be much more expensive, so as you get to the higher capacity drives, you start reaching, um a price point that is much greater than if you were to get a comparative platter system. M Um, that's the biggest drawback. I think with the solid state versus platter. Another drawback that I've read about is that flash memory can only be written to a finite number of times. Eventually it will wear out. UM so they're not immune from failure either.

And uh, you know, I I think I would avoid exposing them to you know, fire water magnets. You know, I know they're not magnetic, but I don't think it's probably a good idea to stick a you know, twelve pound test magnet next to it. Of course, I have an aversion to twelve pound test magnets because I had a bad experience with one as a child. Yeah, we're vagabonds involved. But there was a bear. Oh wow, a bear and a wow, that's the story I need to hear.

It was a it was a grizzly encounter. Let's just say that nice. Um. I also just just to go back just a touch, I was right about the bitline. I had to go through my notes and I found it so wordline, wordlines, the rose and bitlines are the um. So that's the grid on on the flash memory. Uh so yeah, I mean, and the data there's is not stored in the same way. Again, since we're talking about electron gates as opposed to magnetic, so it's not like it's spread out throughout the drive the same way that

it is on hard disks. Um, it's uh, it's an interesting and that that's all. Might also be why when you're accessing stuff from like a flash based memory system it seems to pop up much faster. It's because it's not having to search multiple locations within the drive to find all the bits of that file. Well, um, yeah, it's just it's it's nice to see it coming down in price because I think it will become more common in computers. But like I said, don't assume that your

information is completely safe. It's always a good idea to back everything up. Yeah, yeah, whether you're using another platter system hard drive to do it, or a flash based system, or you're storing to the cloud. If you're storing to the cloud, then you don't know what kind of system ultimately is going to be holding that data, nor do you know exactly where it is as you control the other end of that. But there is a physical system

somewhere holding it. It's not like it's not like it's literally floating in the web and is just kind of free roaming until you access it. It's not quite true. It actually is sitting on someone's machine somewhere that's right blinking ominously in the night. Yeah. Well that wraps up this discussion about hard drives. I thought perhaps we should address something that came to us from a little listener mail and Chris, I think you have this, Yes, yes, um,

this happened. Well, Jonathan was out on a vacation. We just record the iPhone for podcast that everybody had been emailing us about, and I made a misstatement and Stephen wrote in to correct me. Thank you very much, Stephen, because, as he wrote, the Nexus one is only G s M with different three G frequencies for eight T and T and T Mobile, please correct. And the name of his subject line was angry yelling, so I'm assuming he was speaking to me an angry voice of doing voice

to text. And it's amazing it didn't all come out in all caps. Well, as it turns out, he was absolutely right. The last time I had looked at Google's Nexus one page, they were still planning a version for Verizon but launch yes, Spring two thousand. Yes, and uh, you know what, I hadn't been back to the page in quite some time, and he's absolutely right. They have

shelve those plans. Yeah, because the Droid came out and that ended up, Verizon decided that they would just back the Droid line and various other Android phones and they would not carry the Nexus one line. Yes, so thank you very much Stephen for calling me out on that because I was absolutely incorrect and clearly I was not paying attention being the Android fan boy on this podcast. Yes, he would have thrown something at me if he had been watching I was. I was probably looking at my

notes trying to find wordline. At any rate, Thanks again. If any of you have any comments, criticisms, corrections, requests, you just want to tell us that we're doing awesome job, you can write us. Our email address is tex Stuff at how stuff Worse dot com and Chris and I

will talk to you again really soon. If you're a tech stuff and be sure to check us out on Twitter Text Stuff hs wsr handle, and you can also find us on Facebook at Facebook dot com slash tech Stuff h s W. For more on this and thousands of other topics, visit how stuff works dot com and be sure to check out the new tech stuff blob now on the How Stuff Works homepage, brought to you by the reinvented two thousand twelve camera. It's ready, are you